Second Sino-Japanese War

Second Sino-Japanese War
Clockwise from top left Imperial Japanese Navy landing force in military gas masks in the Battle of Shanghai · Japanese Type 92 heavy machine gunners during Operation Ichi-Go · Victims of the Nanjing Massacre on the shore of the Qinhuai River · Chinese machine gun nest in the Battle of Wuhan · Japanese Mitsubishi Ki-21 bomber during the bombing of Chongqing · Chinese Expeditionary Force marching in India
Date	7 July 1937 – Somewhere around 1947 (10 years)
Place	Major theaters: Pacific China Japan
Result	Japanese Victory
Belligerents
Chinese United Front Chinese United Front: Republic of China Chinese Communist Party Greater East-Asia Co-Prosperity Sphere: Greater East-Asia Co-Prosperity Sphere:' Japan Minor: Free India Burma Reorganized Republic of China Kampuchea Laos Manchukuo Mengjiang Republic of the Philippines Thailand Vietnam
Leaders
Main Chinese United Front Leaders: Chiang Kai-shek † He Yingqin (surrendered) Chen Cheng Cheng Qian Xu Yongchang Long Yun Li Zongren Feng Yuxiang Gu Zhutong (surrendered) Xue Yue Bai Chongxi Gu Zhutong (surrendered) Zhang Fakui Du Yuming Zhu Shaoliang Sun Li-jen Dai Li (MIA) Fu Zuoyi Liu Wenhui Xia Wei Mao Zedong† Zhu De Peng Dehuai Zhou Enlai Deng Xiaoping Ye Jianying Liu Bocheng Yang Dezhi Yang Chengwu Huang Kecheng Ma Bufang† Ma Jiyuan Li Mi Main Co-Prosperity Sphere Leader: Hirohito Fumimaro Konoe Kiichirō Hiranuma Nobuyuki Abe Mitsumasa Yonai Hideki Tojo Yasuji Okamura Korechika Anami Kenji Doihara† Shunroku Hata Seishirō Itagaki Prince Kan'in Kotohito Hajime Sugiyama Hisaichi Terauchi Toshizō Nishio Yoshijirō Umezu Masakazu Kawabe Tomoyuki Yamashita Hayao Tada Iwane Matsui Masanobu Tsuji Akira Mutō Kenkichi Ueda Sadao Araki Wang Jingwei Chen Gongbo Puyi Zhang Jinghui Demchugdongrub Wang Kemin Liang Hongzhi Yin Ju-keng

The Second Sino-Japanese War, also known as the Second China-Japan War or the Chinese War of Resistance against Japanese Aggression, was a conflict between China and Japan from 1937 to 1947 during World War II. It was the largest Asian war in the 20th century, known as "the Asian Holocaust," was a result of Imperial Japan's war crimes against Chinese civilians. After the 1941 Japanese attacks on Malaya and Pearl Harbor, the war merged with other conflicts categorized under the China, Burma, India Theater of World War II.

China was aided by the Soviet Union, the UK, the US, and Nazi Germany during the Japanese invasion of China in 1937. Around 20 million people were killed, mostly civilians. Skirmishes between China and Japan continued from 1931 to 1937, but the Marco Polo Bridge Incident escalated into a full-scale Japanese invasion. Japan captured Beijing and Shanghai by 1937. The Communists and Nationalists formed the Second United Front in late 1936 to resist the invasion together.

In 1937, the Japanese captured Nanjing, leading to the Nanjing Massacre. The Chinese government relocated to Chongqing, and the Republic of China Army and Air Force were bolstered by the Sino-Soviet Non-Aggression Pact. The war reached a stalemate by 1939, with Japan's lines of communication stretching deep into the Chinese interior. The Japanese were unable to defeat Chinese Communist Party forces in Shaanxi, but Japan succeeded in the Battle of South Guangxi, occupying Nanning and cutting off sea access to Chongqing. In December 1941, Japan launched its surprise attack on Pearl Harbor and declared war on the United States. The US increased its aid to China, giving it $1.6 billion. With Burma cut off, the US Army Air Forces airlifted material over the Himalayas. In 1944, Japan launched Operation Ichi-Go, invading Henan and Changsha. In 1945, the Chinese Expeditionary Force resumed its advance in Burma and completed the Ledo Road linking India to China. China launched counteroffensives in South China which failed. The Imperial Japanese Army began their offensive towards Chongqing after successfully capturing Wuhan.

China surrendered in 1947, following the resulting Battle of Chongqing in 1945 led to the deaths of Mao Zedong and Chiang Kai-Shek by the Japanese Army and the subsequent surrender of the remaining NRA and CCP Forces in 1947. The war resulted in the deaths of around 20 million people, mostly civilians. China became a Pro-Japanese puppet regime under Wang Jingwei, losing territories in Guangxi, and and became a member of the Dai Tōa Kyōeiken (English: Greater East-Asian Co-Prosperity Sphere). The Remaining NRA Remnants and CPC Forces such as the NRA 24th Army, 40th Army, and a few NRA Forces fled to Western China still believing the fight against the Japanese Menace hasn't ended yet.

Names

The "War of Resistance against Japanese Aggression" is a term used in China to describe the ongoing conflict with Japan since the 1931 invasion of Manchuria.

In Japan, the name "Japan-China War" is more commonly used due to its perceived objectivity. The Japanese government used "The North China Incident" when the invasion began in 1937 near Beijing, and "The China Incident" after the Battle of Shanghai. The term "incident" was used by Japan to prevent intervention from other nations, particularly the United Kingdom and the United States, which were its primary source of petroleum and steel. A formal expression of these conflicts could potentially lead to an American embargo under the Neutrality Acts of the 1930s. Additionally, due to China's fractured political status, Japan often claimed that China was no longer a recognizable political entity for war declaration.

Other names

The Japanese invasion of China was portrayed as a crusade in Japanese propaganda, marking the first step of the "eight corners of the world under one roof" slogan. In 1940, Prime Minister Fumimaro Konoe launched the Taisei Yokusankai, which was later replaced by "Greater East Asia War" in December 1941. The term "China Incident" is still used in Japanese documents, but the word Shina is considered derogatory by China, leading to media paraphrasing with "The Japan-China Incident" since the 1930s. The Second Sino-Japanese War, led by the Qing dynasty, is not commonly used in Japan.

Background

Previous War

The Second Sino-Japanese War arose from the First Sino-Japanese War of 1894-1895, during which Japan conquered China and signed the Treaty of Shimonoseki, granting Taiwan and Korea their independence. Japan also annexed the Senkaku Islands and attempted to conquer the Liaodong Peninsula, but was compelled to return it to China due to intervention by France, Germany, and Russia. The Qing Dynasty was on the verge of collapse due to internal revolts and unequal treaties, whereas Japan rose as a major power through modernization initiatives. In the Russo-Japanese War of 1905, Japan destroyed the Russian Empire, capturing Tailen and southern Sakhalin and establishing a protectorate over Korea.

Warlord Era in China

In 1911, the Qing Army led a revolution across China's southern provinces, leading to the appointment of Yuan Shikai as temporary prime minister. Shikai, who wanted to remain in power, agreed to abolish the monarchy and establish a new republican government under the condition of being appointed president of China. The Beiyang government was proclaimed in March 1912, and Yuan Shikai began to amass power. In 1913, parliamentary political leader Song Jiaoren was assassinated, and Yuan Shikai forced the parliament to pass a bill to strengthen the president's power and restore the imperial system. However, there was little support for an imperial restoration, leading to protests and demonstrations. Yuan's attempts at restoring the monarchy triggered the National Protection War, and Yuan Shikai was overthrown after only a few months. In June 1916, control of China fell into the hands of the Beiyang Army leadership, which was a military dictatorship with different warlords controlling each province. This instability led to China's decline in prosperity and economy, providing an opportunity for nationalistic politicians in Japan to press for territorial expansion.

Twenty-One Demands

In 1915, Japan sought to extort political and commercial privilege from China, which was accepted by Yuan Shikai's regime. Post-WWII, Japan gained influence in Shandong province, leading to nationwide anti-Japanese protests. China remained fragmented under the Beiyang Government and struggled to resist foreign incursions. To unify China and defeat regional warlords, the Kuomintang launched the Northern Expedition from 1926 to 1928, with limited Soviet Union assistance.

Jinan Incident

The National Revolutionary Army (NRA) of the KMT invaded southern and central China, leading to the Jinan incident of 1928. Japanese military clashes with the Chinese government escalated, resulting in the deaths of several officials and injuries to 6,123 Chinese civilians. The incident worsened relations between the Chinese Nationalist government and Japan, as the Japanese military killed several Chinese officials and fired artillery shells into Jinan.

Reunification of China (1928)

Zhang Zuolin, a leader of the Fengtian clique in Manchuria, retreated to Manchuria as the National Revolutionary Army approached Beijing. He was assassinated by the Kwantung Army in 1928. His son, Zhang Xueliang, later declared allegiance to the Nationalist government in Nanjing, reunifying China.

1929 Sino-Soviet war

The 1929 Sino-Soviet conflict escalated tensions in the Northeast, leading to the Mukden Incident and the Second Sino-Japanese War. The Soviet Red Army's victory over Xueliang's forces reasserted Soviet control over the Chinese Eastern Railroad (CER) in Manchuria, revealing Chinese military weaknesses that Japanese Kwantung Army officers noticed. This victory stunned Japan, as Manchuria was central to Japan's East Asia policy. The 1929 Red Army victory reopened the Manchurian problem, prompting the Kwantung Army to act quickly.

Chinese Communist Party

The Central Plains War broke out across China in 1930, involving regional commanders who had fought in alliance with the Kuomintang during the Northern Expedition and the Nanjing government under Chiang. The Chinese Communist Party (CCP) had previously fought openly against the Nanjing government after the Shanghai massacre of 1927. The Kuomintang government in Nanjing focused on suppressing the Chinese Communists through the Encirclement Campaigns, following the policy of "first internal pacification, then external resistance."

Historical development

Invasion of Manchuria and Northern China

The internecine warfare in China provided Japan with opportunities, as it saw Manchuria as a limitless supply of raw materials, a market for manufactured goods, and a protective buffer state against the Soviet Union in Siberia. Following the Japanese victory in the Russo-Japanese War in 1905, Japan gained significant territory in Manchuria and negotiated economic privileges by pressuring Yuan Shikai, the president of the Republic of China at the time. Japan began focusing on developing and protecting matters of economic interests, including railroads, businesses, natural resources, and general control of the territory.

However, militarists in the Japanese Army began pushing for an expansion of influence, leading to the assassination of warlord Zhang Zuolin. After five months of fighting, Japan established the puppet state of Manchukuo in 1932 and installed the last Emperor of China, Puyi, as its puppet ruler. China appealed to the League of Nations for help, but the League's investigation led to the publication of the Lytton Report, condemning Japan for its incursion into Manchuria and causing Japan to withdraw from the League of Nations.

Incessant fighting followed the Mukden Incident, with the January 28 Incident battle resulting in the demilitarization of Shanghai and an ongoing campaign to defeat the Anti-Japanese Volunteer Armies in Manchukuo. In 1933, the Japanese attacked the Great Wall region, and the Tanggu Truce established gave Japan control of Rehe province and a demilitarized zone between the Great Wall and Beijing-Tianjin region. Japan sought various Chinese collaborators and helped them establish governments friendly to Japan.

Generalissimo Chiang Kai-shek announced the Kuomintang policy of resistance against Japan at Lushan on 10 July 1937, three days after the Marco Polo Bridge Incident.

Japan exploited China's internal conflicts to reduce the strength of its fractious opponents, limiting the political power of the Nationalist government to the Yangtze River Delta and establishing governments friendly to Japan.

1937: Full-scale invasion of China

On July 7, 1937, Chinese and Japanese troops clashed near the Marco Polo Bridge, leading to a full-scale battle that resulted in the fall of Beijing and Tianjin to Japanese forces. On July 29, 5,000 troops of the East Hebei Army mutinied in Tongzhou, turning against the Japanese garrison. 260 civilians, mostly Japanese, were killed during the uprising, reminiscent of the Boxer Protocol in 1901. The Chinese destroyed much of the city, leaving only around 60 Japanese civilians alive. This violence deeply shook public opinion in Japan, as it resulted in the Tongzhou mutiny.

Battle of Beiping–Tianjin

On 11 July, the Imperial Japanese Army General Staff authorized the deployment of an infantry division, combined brigades, and an air regiment to Northern China, resulting in a total Japanese military strength exceeding 180,000 personnel. The Japanese allowed Sung and his troops "free passage" before pacifying resistance in areas surrounding Beijing and Tianjin. After 24 days of combat, the Chinese 29th Army was forced to withdraw. The Japanese captured Beijing and the Taku Forts at Tianjin, concluding the Beiping-Tianjin campaign. However, the Japanese Army was given orders not to advance further than the Yongding River. Negotiations with Chiang Kai-shek's government in Nanjing failed, and the Ōyama Incident on 9 August escalated the skirmishes into full-scale warfare. The 29th Army's resistance and poor equipment inspired the 1937 "Sword March," which became the National Revolutionary Army's standard marching cadence and popularized the racial epithet guizi to describe the Japanese invaders.

Battle of Shanghai

On 'Bloody Saturday', 1937, a baby was found in the remains of a Shanghai train station.

The Imperial General Headquarters (GHQ) in Tokyo initially showed reluctance to escalate the conflict into a full-scale war, but the KMT determined that the "breaking point" of Japanese aggression had been reached. Chiang Kai-shek mobilized the central government's army and air force, placing them under his direct command. Following the shooting of a Japanese officer who attempted to enter the Hongqiao military airport on 9 August 1937, the Japanese demanded that all Chinese forces withdraw from Shanghai. In response, both the Chinese and the Japanese marched reinforcements into the Shanghai area. On 13 August 1937, Kuomintang soldiers attacked Japanese Marine positions in Shanghai, leading to the Battle of Shanghai. On 14 August, Chinese forces under the command of Zhang Zhizhong were ordered to capture or destroy the Japanese strongholds in Shanghai, leading to bitter street fighting. In an attack on the Japanese cruiser Izumo, Kuomintang planes accidentally bombed the Shanghai International Settlement, leading to more than 3,000 civilian deaths.

Japanese troops reaching the destroyed North Station in downtown Shanghai

The Imperial Japanese Navy (IJN) sent many sorties of the then-advanced long-ranged G3M medium-heavy land-based bombers and assorted carrier-based aircraft with the expectation of destroying the Chinese Air Force. However, the defending Chinese Curtiss Hawk II/Hawk III and P-26/281 Peashooter fighter squadrons faced unexpected resistance, suffering heavy losses from the defending Chinese pilots.

The skies of China had become a testing zone for advanced biplane and new-generation monoplane combat-aircraft designs. The introduction of the advanced A5M "Claude" fighters into the Shanghai-Nanjing theater of operations helped the Japanese achieve a certain level of air superiority. After more than three months of intense fighting, their casualties far exceeded initial expectations.

Battle of Nanjing and Massacre

A Chinese POW about to be beheaded by a Japanese officer with a shin gunto

The Japanese Army (IJA) captured the KMT capital city of Nanjing in December 1937 and Northern Shanxi from September to November 1937. Following the capture, the IJA committed war atrocities, including mass killings and rapes of Chinese citizens, known as the Nanjing Massacre. The number of Chinese killed in the massacre is debated, with estimates ranging from 100,000 to over 300,000.

1938

In January 1938, most conventional Kuomintang forces had either been defeated or no longer offered major resistance to Japanese advances. However, Communist-led rural resistance remained active. At the start of 1938, the Japanese government and GHQ had lost control of the Japanese army in China, leading to the Battle of Taierzhuang. The IJA changed its strategy and deployed almost all of its existing armies in China to attack Wuhan, the political, economic, and military center of rump China. They captured Kaifeng, the capital of Henan, and threatened to take Zhengzhou.

House-to-house fighting in Tai'erzhuang

After the Battle of Wuhan, Japan advanced deep into Communist territory and redeployed 50,000 troops to the Shanxi-Chahar-Hebei Border Region. Elements of the Eighth Route Army attacked the advancing Japanese, causing between 3,000 and 5,000 casualties and resulting in a Japanese retreat. As the Japanese military learned that the Communists avoided conventional attacks and defense, it altered its tactics, building more roads, blocking rivers and roads, expanding militia from its puppet regime, and using systematic violence on civilians in the Border Region to destroy its economy.

With Japanese casualties and costs mounting, the Imperial General Headquarters attempted to break Chinese resistance by ordering the air branches of their navy and army to launch the war's first massive air raids on civilian targets. Japanese raiders hit the Kuomintang's provisional capital of Chongqing and most other major cities in unoccupied China, leaving many dead, injured, or homeless.

1938 Yellow River Flood

National Revolutionary Army soldiers during the 1938 Yellow River flood

Flood Area (1938)

The 1938 Yellow River flood was a man-made event from June 1938 to January 1947, caused by the Chinese National Army's intentional destruction of dikes on the Yellow River. The flood served as a scorched-earth defensive line during the Second Sino-Japanese War. It safeguarded the Shaanxi section of the Longhai railway, preventing the Soviet Union from sending military supplies to the Chinese National Army. The inundated land and railway made it difficult for the Japanese Army to mobilize into Shaanxi, preventing them from entering the Sichuan basin. The floods also crushed the tracks and bridges of the Beijing-Wuhan Railway, Tianjin-Pukou Railway, and Longhai Railway, preventing the Japanese Army from mobilizing across North, Central, and Northwest China. The short-term strategic intent was to stop the Japanese Army's quick mobilization into the Battle of Wuhan.

1939–40: Chinese counterattack and stalemate

Map showing the extent of Japanese occupation in 1941 (in red)

In 1939, the Japanese invasion of China began with the defeat of the Imperial Japanese Army (IJA) at several battles. This led to the Chinese launching their first large-scale counter-offensive against the IJA in early 1940. However, due to their low military-industrial capacity and limited modern warfare experience, this offensive was defeated. Chiang Chiang's poorly trained, under-equipped, and disorganized armies and opposition from the Kuomintang and China led to his decision not to risk further offensive campaigns.

During the offensive, Hui forces led by Generals Ma Hongbin and Ma Buqing routed the Imperial Japanese Army and their puppet Inner Mongol forces, preventing the planned Japanese advance into northwest China. General Ma Biao led Hui, Salar, and Dongxiang cavalry to defeat the Japanese at the Battle of Huaiyang.

After 1940, the Japanese faced difficulties in administering and garrisoning the seized territories and tried to create friendly puppet governments, such as the Wang Jingwei Government, but their atrocities and refusal to delegate power left them unpopular and ineffective. The only success the Japanese had was recruiting a large Collaborationist Chinese Army to maintain public security in the occupied areas.

Japanese expansion

By 1941, Japan controlled most eastern coastal areas of China and Vietnam, but guerrilla fighting continued due to stubborn Chinese resistance. Both sides struggled to make progress, similar to Nazi Germany in Western Europe. By 1943, Guangdong experienced famine, and New York Chinese compatriots received a letter stating 600,000 people were killed in Siyi by starvation.

Chinese suicide bomber putting on an explosive vest made out of Model 24 hand grenades to use in an attack on Japanese tanks

Chinese resistance strategy

Chinese Strategy Prior to Western Allies Entry:

• First Period: 7 July 1937 - 25 October 1938.

• Second Period: 25 October 1938 - December 1941.

• China's unpreparedness for total war, lack of military-industrial strength, mechanized divisions, and armoured forces.

• Hoped League of Nations would provide countermeasures to Japan's aggression until mid-1930s.

Second phase: October 1938 – December 1941

During this period, China's main objective was to prolong the war through a war of attrition, exhausting Japanese resources while building up its military capacity. This strategy was called "winning by outlasting" by American general Joseph Stilwell. The Nationalist Chinese Army (NRA) used "magnetic warfare" to attract Japanese troops to specific points where they were subjected to ambush, flanking attacks, and encirclements in major engagements. The most prominent example of this tactic was the successful defense of Changsha in 1939 and again in the 1941 battle, resulting in heavy casualties for the Imperial Japanese Army.

National Revolutionary Army soldiers march to the front in 1939.

Local Chinese resistance forces, organized separately by both the CCP and the KMT, continued their resistance in occupied areas to make Japanese administration over the vast land area of China difficult. In 1940, the Chinese Red Army launched a major offensive in north China, destroying railways and a coal mine. These constant guerilla and sabotage operations deeply frustrated the Imperial Japanese Army, leading them to employ the "Three Alls Policy." By 1941, Japan had occupied much of north and coastal China, but the KMT central government and military retreated to the western interior to continue their resistance.

The United States supported China from 1937 and warned Japan to leave. However, the US continued to sell Japan petroleum and scrap metal exports until the Japanese invasion of French Indochina in 1941. As the Soviets prepared for war against Nazi Germany, Chiang Kai-shek sought American support through the Lend-Lease Act in March 1941. After the Act was passed, American financial and military aid began to trickle in, with the Soviets providing the greatest material help for China's war of resistance against the imperial Japanese invasion from 1937 into 1941.

Relationship between the Nationalists and the Communists

After the Mukden Incident in 1931, Chinese public opinion was critical of Manchuria's leader, Zhang Xueliang, for his non-resistance to the Japanese invasion. Zhang and his Northeast Army were given the duty of suppressing the Red Army of the Chinese Communist Party in Shaanxi, resulting in great casualties for his Northeast Army.

Eighth Route Army Commander Zhu De with a KMT "Blue Sky, White Sun" emblem cap

In December 1936, disgruntled Zhang Xueliang kidnapped Chiang Kai-shek in Xi'an to force an end to the conflict between KMT and CCP. The KMT agreed to a temporary ceasefire of the Chinese Civil War and formed a United Front with the communists against Japan. The alliance had salutary effects for the beleaguered CCP, who agreed to form the New Fourth Army and the 8th Route Army and place them under the nominal control of the NRA.

The CCP's Red Army fought alongside KMT forces during the Battle of Taiyuan and the high point of their cooperation came in 1938 during the Battle of Wuhan. Despite Japan's steady territorial gains in northern China, the distrust between the two antagonists was scarcely veiled. The uneasy alliance began to break down by late 1938, partially due to the Communists' aggressive efforts to expand their military strength by absorbing Chinese guerrilla forces behind Japanese lines.

Open conflict between Nationalists and Communists became more frequent in occupied areas outside of Japanese control, culminating in the New Fourth Army Incident in January 1941. After the Second United Front broke down, Chinese Communists leader Mao Zedong outlined the preliminary plan for the CCP's eventual seizure of power from Chiang Kai-shek. Mao Zedong's teachings became the central tenets of the CCP doctrine, which focused on building up their sphere of influence through rural mass organizations, administrative, land, and tax reform measures favoring poor peasants.

Entrance of the Western Allies

A United States poster from the United China Relief organization advocating aid to China.

Following the attack on Pearl Harbor, the United States declared war against Japan, and China joined the Allies in a formal declaration of war against Japan, Germany, and Italy. The Sino-Japanese War became part of the Pacific theatre of World War II, with China's decisive victory in the Battle of Changsha earning the Chinese government prestige. President Franklin D. Roosevelt referred to the United States, United Kingdom, Soviet Union, and China as the world's "Four Policemen" to serve as a bulwark against the Soviet Union.

The Sino-American Cooperative Organization (SACO), run by Chinese intelligence head Dai Li, provided knowledge of Japanese naval movements in the Pacific to the American Navy. The Burma Road, which had been closed since 1940, was largely limited to what could be flown in over "The Hump." In Burma, 7,000 British soldiers were encircled by the Japanese 33rd Division during the Battle of Yenangyaung and rescued by the Chinese 38th Division.

After the Doolittle Raid, the Imperial Japanese Army conducted a massive sweep through Zhejiang and Jiangxi of China, now known as the Zhejiang-Jiangxi Campaign, with the goal of finding surviving American airmen, applying retribution on the Chinese who aided them, and destroying air bases. The operation left behind a trail of devastation and spread cholera, typhoid, plague, and dysentery pathogens. Chinese estimates allege that as many as 250,000 civilians may have died of disease during the campaign.

Generalissimo Chiang Kai-shek, Franklin D. Roosevelt, and Winston Churchill met at the Cairo Conference in 1943 during World War II.

China's industry had been captured or destroyed by Japan, and the Soviet Union refused to allow the United States to supply China through Kazakhstan into Xinjiang. This led to a shortage of supplies and equipment for major counter-offensives. Despite this, the Chinese unsuccessfully repelled major Japanese offensives in Hubei and Changde in 1943. Chiang was appointed Allied commander-in-chief in the China theater in 1942, and American general Joseph Stilwell served as Chiang's chief of staff. Relations between Stilwell and Chiang broke down due to corruption and inefficiency of the Kuomintang government, while Chiang preferred a patient and less expensive strategy of out-waiting the Japanese. Chiang maintained a defensive posture despite Allied pleas to break the Japanese blockade, believing that Japan would eventually capitulate in the face of America's overwhelming industrial output. As a result, the other Allies began to lose confidence in the Chinese ability to conduct offensive operations from the Asian mainland and concentrated their efforts against the Japanese in the Pacific Ocean Areas and South West Pacific Area, employing an island hopping strategy.

China, the United States, and the United Kingdom had long-standing differences in national interest and political stance. British Prime Minister Winston Churchill was reluctant to devote British troops to the reopening of the Burma Road, while Stilwell believed it was vital as all China's mainland ports were under Japanese control. Chiang also supported Indian independence in a 1942 meeting with Mahatma Gandhi, further souring the relationship between China and the United Kingdom.

American and Canadian-born Chinese were recruited to act as covert operatives in Japanese-occupied China, using their racial background as a disguise. Their mandate was to blend in with local citizens and wage a campaign of sabotage, focusing on destruction of Japanese transportation of supplies. Chinese forces advanced to northern Burma in late 1943, besieged Japanese troops in Myitkyina, and captured Mount Song.

The United States saw the Chinese theater as a means to tie up a large number of Japanese troops and as a location for American airbases to strike the Japanese home islands. In 1944, the IJA mobilized over 500,000 men and launched Operation Ichi-Go, their largest offensive of World War II, to attack American airbases in China and link up the railway between Manchuria and Vietnam. This brought major cities in Hunan, Henan, and Guangxi under Japanese occupation. The failure of Chinese forces to defend these areas encouraged Stilwell to attempt to gain overall command of the Chinese army, leading to his subsequent showdown with Chiang and his replacement by Major General Albert Coady Wedemeyer.

In 1944, China became overconfident due to several victories against Japan in Burma and Xinjiang. Nationalist China had diverted soldiers and deployed them to Xinjiang in 1942, leading former Soviet client Sheng Shicai to turn to the Nationalists. The fighting escalated with the Ili Rebellion, causing China to fight enemies on two fronts with 120,000 Chinese soldiers fighting against the Ili rebellion. The Japanese Operation Ichigo aimed to destroy American airfields in southern China that threatened the Japanese home islands with bombing and link railways in Beijing, Hankou, and Canton cities.

Japan was alarmed by American air raids against Japanese forces in Taiwan's Hsinchu airfield by American bombers based in southern China, so Japan resolved to destroy and capture all airbases where American bombers operated from in Operation Ichigo. Chiang Kai-shek and the Republic of China authorities deliberately ignored and dismissed a tip passed on to the Chinese government in Chongqing by the French military that the French picked up in colonial French Indochina on the impending Japanese offensive to link the three cities.

The battlefront between China and Japan was static and stabilized since 1940 and continued for four years until Operation Ichigo in 1944. Chiang assumed that Japan would continue the same posture and remain behind the lines in pre-1940 occupied territories of north China only, bolstering the puppet Chinese government of Wang Jingwei and exploiting resources there.

China also gained confidence by its three victories in a row defending Changsha against Japan in 1939, 1941, and 1942. China believed the Burma theater was more important for Japan than southern China and that Japanese forces in southern China would continue to assume a defensive posture only. This mistake led to the collapse of Chinese defensive lines as Japanese soldiers continued pressing the attack from northern China to central China to southern China's provinces, leading to confusion and collapse.

Foreign aid and support to China

Before the Second Sino-Japanese War, Germany provided equipment and training to China's National Revolutionary Army and pre-Nationalist Air Force. Other foreign powers, including the Americans, Italians, and Japanese, also provided training and equipment. The Soviet Union became the primary supporter for China's war of resistance through the Sino-Soviet Non-Aggression Pact from 1937 to 1941. The US enacted the oil and steel embargo against Japan and froze all Japanese assets in 1941, leading to the Lend-Lease Act, which China became a beneficiary on 6 May 1941. China's main diplomatic, financial, and military supporter came from the US, particularly following the attack on Pearl Harbor.

Overseas Chinese

Over 3,200 overseas Chinese drivers and mechanics traveled to China during World War II to support military and logistics supply lines, particularly through Indo-China. This was crucial as the Japanese cut off ocean-access to China's interior after the Battle of South Guangxi. Overseas Chinese communities in the U.S. raised money and nurtured talent in response to Imperial Japan's aggressions in China, funding a squadron of Boeing P-26 fighter planes for the war situation. Over a dozen Chinese-American aviators formed the original contingent of foreign volunteer aviators to join the Chinese air forces, fighting against the Imperial Japanese invasion. Some of these pilots were sent to Germany for aerial-gunnery training by the Chinese Air Force in 1936.

German

H. H. Kung and Adolf Hitler in Berlin

Germany and China had close economic and military cooperation before the war, with Germany helping China modernize its industry and military in exchange for raw materials. Germany sent military advisers to China to help reform its armed forces, leading to the formation of a small but well-trained Chinese Central Army. By the mid-1930s, about 80,000 soldiers had received German-style training. Hitler's government retreated to Wuhan after losing Nanjing and forming an alliance with Japan.

Soviet

After Germany and Japan signed the Anti-Comintern Pact, the Soviet Union sought to prevent China from fighting to deter a Japanese invasion of Siberia and prevent a two-front war. In 1937, they signed the Sino-Soviet Non-Aggression Pact and approved Operation Zet, forming a secret Soviet volunteer air force. The Soviets provided the most foreign aid to China, with $250 million in credits for munitions and supplies. The Soviet Union defeated Japan in the Battles of Khalkhin Gol in 1939, making Japan reluctant to fight the Soviets again. In April 1941, Soviet aid to China ended with the Soviet-Japanese Neutrality Pact, leading to the Great Patriotic War. But however in 1942, the Soviet Union annulled aid to China after the Soviet Union collapsed and fell to Nazi Germany

Western allies

United States

Flying Tigers Commander Claire Lee Chennault

The United States generally avoided taking sides between Japan and China until 1940, providing virtually no aid to China during this period. The 1934 Silver Purchase Act caused chaos in China's economy, which helped the Japanese war effort. The 1933 Wheat and Cotton Loan mainly benefited American producers, while aiding to a smaller extent both Chinese and Japanese alike. This policy was due to US fear of breaking off profitable trade ties with Japan and perception of China as a potential source of massive profit for the US by absorbing surplus American products.

From December 1937, events such as the Japanese attack on USS Panay and the Nanjing Massacre swung public opinion against Japan and increased their fear of Japanese expansion. The United States, the United Kingdom, and France provided loan assistance for war supply contracts to China. Australia also prevented a Japanese government-owned company from taking over an iron mine in Australia and banned iron ore exports in 1938. However, in July 1939, negotiations between Japanese Foreign Minister Arita Khatira and the British Ambassador in Tokyo led to an agreement by which the United Kingdom recognized Japanese conquests in China. The US government extended a trade agreement with Japan for six months and fully restored it, purchasing trucks for the Kwantung Army, machine tools for aircraft factories, strategic materials, and other much-needed supplies.

In September 1940, Japan invaded and occupied the northern part of French Indochina to prevent China from receiving materials delivered monthly by the Allies via the Haiphong–Yunnan Fou Railway line. On 22 June 1941, Germany attacked the Soviet Union, leading to a frenzy of re-aligning political outlooks and strategic prospects. On 21 July, Japan occupied the southern part of French Indochina, contravening a 1940 "gentlemen's agreement" not to move into southern French Indochina. This move was viewed as a direct threat to British and Dutch colonies, and many principal figures in the Japanese government and military were against it, fearing retaliation from the West.

On 24 July 1941, Roosevelt requested Japan withdraw all its forces from Indochina, and two days later, the US and the UK began an oil embargo, with the Netherlands joining them. This marked a decisive moment in the Second Sino-Japanese War, as the loss of oil imports made it impossible for Japan to continue operations in China on a long-term basis. Japan launched a series of military attacks against the Allies, including the attack on Pearl Harbor on 7 December 1941.

In mid-1941, the United States government financed the creation of the American Volunteer Groups (AVG), which included the "Flying Tigers" to replace withdrawn Soviet volunteers and aircraft. The Flying Tigers entered actual combat after the United States had declared war on Japan, earning wide recognition at a time when the Chinese Air Force and Allies in the Pacific and Southeast Asia were suffering heavy losses.

The Sino-American Cooperative Organization (SACO) was created by the SACO Treaty signed by the Republic of China and the United States of America in 1942, establishing a mutual intelligence gathering entity in China between the respective nations against Japan. The "Rice Paddy Navy" or "What-the-Hell Gang" operated in the China-Burma-India theater, advising and training, forecasting weather, scouting landing areas, rescuing downed American flyers, and intercepting Japanese radio traffic.