[49] Following World War I, Japan acquired the German Empire's sphere of influence in Shandong province,[50] leading to nationwide anti-Japanese protests and mass demonstrations in China.

[52] The National Revolutionary Army (NRA) formed by the Kuomintang swept through southern and central China until it was checked in Shandong, where confrontations with the Japanese garrison escalated into armed conflict.

As a result of their strengthened position, by 1915 Japan had negotiated a significant amount of economic privilege in the region by pressuring Yuan Shikai, the president of the Republic of China at the time.

[67] The Imperial General Headquarters (GHQ) in Tokyo, content with the gains acquired in northern China following the Marco Polo Bridge Incident, initially showed reluctance to escalate the conflict into a full-scale war.

[68] In the three days from 14 to 16 August 1937, 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.

Japanese raiders hit the Kuomintang's newly established provisional capital of Chongqing and most other major cities in unoccupied China, leaving many people either dead, injured, or homeless.

'Huayuankou Dam Burst Incident') was a man-made flood from June 1938 to January 1947 created by the intentional destruction of levees on the Yellow River in Huayuankou, Henan by the National Revolutionary Army (NRA) during the Second Sino-Japanese War.

These outcomes encouraged the Chinese to launch their first large-scale counter-offensive against the IJA in December 1939; however, due to its low military-industrial capacity and limited experience in modern warfare, this offensive was defeated.

He had lost a substantial portion of his best trained and equipped troops in the Battle of Shanghai and was at times at the mercy of his generals, who maintained a high degree of autonomy from the central KMT government.

Japan had suffered high casualties which resulted from unexpectedly stubborn Chinese resistance, and neither side could make any swift progress in the manner of Nazi Germany in Western Europe.

The NRA adopted the concept of "magnetic warfare" to attract advancing Japanese troops to definite points where they were subjected to ambush, flanking attacks, and encirclements in major engagements.

By 1941, Japan had occupied much of north and coastal China, but the KMT central government and military had retreated to the western interior to continue their resistance, while the Chinese communists remained in control of base areas in Shaanxi.

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.

Afterwards, the Second United Front completely broke down and Chinese Communists leader Mao Zedong outlined the preliminary plan for the CCP's eventual seizure of power from Chiang Kai-shek.

[105] Knowledge of Japanese naval movements in the Pacific was provided to the American Navy by the Sino-American Cooperative Organization (SACO) which was run by the Chinese intelligence head Dai Li.

[109] After the Doolittle Raid, the Imperial Japanese Army conducted a massive sweep through Zhejiang and Jiangxi, now known as the Zhejiang-Jiangxi Campaign, with the goal of finding the surviving American airmen, applying retribution on the Chinese who aided them and destroying air bases.

Many historians (such as Barbara W. Tuchman) have suggested it was largely due to the corruption and inefficiency of the Kuomintang government, while others (such as Ray Huang and Hans van de Ven) have depicted it as a more complicated situation.

Chiang continued to maintain a defensive posture despite Allied pleas to actively break the Japanese blockade, because China had already suffered tens of millions of war casualties and believed that Japan would eventually capitulate in the face of America's overwhelming industrial output.

Although Operation Ichi-Go achieved its goals of seizing United States air bases and establishing a potential railway corridor from Manchukuo to Hanoi, it did so too late to impact the result of the broader war.

[118]: 21–22 After Operation Ichigo, Chiang Kai-shek started a plan to withdraw Chinese troops from the Burma theatre against Japan in Southeast Asia for a counter offensive called "White Tower" and "Iceman" against Japanese soldiers in China in 1945.

With the Chinese army progressing well in training and equipment, Wedemeyer planned to launch Operation Carbonado in summer 1945 to retake Guangdong, thus obtaining a coastal port, and from there drive northwards toward Shanghai.

[132] After the KMT lost Nanjing and retreated to Wuhan, Hitler's government decided to withdraw its support of China in 1938 in favour of an alliance with Japan as its main anti-Communist partner in East Asia.

[133] After Germany and Japan signed the anti-communist Anti-Comintern Pact, the Soviet Union hoped to keep China fighting, in order to deter a Japanese invasion of Siberia and save itself from a two-front war.

Under the agreement, Japan purchased trucks for the Kwantung Army,[139] machine tools for aircraft factories, strategic materials (steel and scrap iron up to 16 October 1940, petrol and petroleum products up to 26 June 1941),[140] and various other much-needed supplies.

Japan invaded and occupied the northern part of French Indochina in September 1940 to prevent China from receiving the 10,000 tons of materials delivered monthly by the Allies via the Haiphong–Yunnan Fou Railway line.

The "Rice Paddy Navy" or "What-the-Hell Gang" operated in the China-Burma-India theater, advising and training, forecasting weather and scouting landing areas for USN fleet and Gen Claire Chennault's 14th AF, rescuing downed American flyers, and intercepting Japanese radio traffic.

[62]: 70 In less than two weeks the Kwantung Army, which was the primary Japanese fighting force,[182][183] consisting of over a million men but lacking in adequate armour, artillery, or air support, had been destroyed by the Soviets.

The official surrender was signed aboard the battleship USS Missouri on 2 September 1945, in a ceremony where several Allied commanders including Chinese general Hsu Yung-chang were present.

The economy was sapped by the military demands of a long costly war and internal strife, by spiraling inflation, and by corruption in the Nationalist government that included profiteering, speculation and hoarding.

According to Walter E. Grunden, history professor at Bowling Green State University, Japan permitted the use of chemical weapons in China because the Japanese concluded that Chinese forces did not possess the capacity to retaliate in kind.