Imperial Japanese Army in the context of "Operation U-Go"

The Empire of Japan, also known as the Japanese Empire or Imperial Japan, was the Japanese nation state that existed from the Meiji Restoration on January 3, 1868, until the Constitution of Japan took effect on May 3, 1947. From August 1910 to September 1945, it included the Japanese archipelago, the Kurils, Karafuto, Korea, and Taiwan. The South Seas Mandate and concessions such as the Kwantung Leased Territory were de jure not internal parts of the empire but dependent territories. In the closing stages of World War II, with Japan defeated alongside the rest of the Axis powers, the formalized surrender was issued on September 2, 1945, in compliance with the Potsdam Declaration of the Allies, and the empire's territory subsequently shrunk to cover only the Japanese archipelago resembling modern Japan.

Under the slogans of "Enrich the Country, Strengthen the Armed Forces" and "Promote Industry" which followed the Boshin War and the restoration of power to the emperor from the shogun, Japan underwent a period of large-scale industrialization and militarization, often regarded as the fastest modernization of any country to date. All of these aspects contributed to Japan's emergence as a great power following the First Sino-Japanese War, the Boxer Rebellion, the Russo-Japanese War, and World War I. Economic and political turmoil in the 1920s, including the Great Depression, led to the rise of militarism, nationalism, statism and authoritarianism, during which Japan joined the Axis alliance with Nazi Germany and Fascist Italy, conquering a large part of the Asia–Pacific; during this period, the Imperial Japanese Army (IJA) and the Imperial Japanese Navy (IJN) committed numerous atrocities and war crimes, including the Nanjing Massacre. There has been a debate over defining the political system of Japan as a dictatorship, which has been disputed due by the absence of a dictator, and over calling it fascist. The other suggested terms were para-fascism, militarism, corporatism, totalitarianism, and police state.

The Marco Polo Bridge incident, also known as the Lugou Bridge incident or the July 7 incident, was a 3-day battle that began on 7 July 1937 in the district of Beijing between the 29th Army of the National Revolutionary Army of the Republic of China and the Imperial Japanese Army.

Since the Japanese invasion of Manchuria in 1931, there had been many small incidents along the rail line connecting Beijing with the port of Tianjin, but all had subsided. On the night of 7 July, Japanese garrison troops at Lugouqiao held an unusual manoeuvre; and, alleging that a Japanese soldier was missing, demanded entry into the City of Wanping to conduct a search. Fighting broke out while the Japanese complaint was still under negotiation. However, the missing Japanese soldier had already returned to his lines. The Marco Polo Bridge incident is generally regarded as the start of the Second Sino-Japanese War.

Hideki Tojo (東條 英機, Tōjō Hideki; pronounced [toːʑoː çideki] ; 30 December 1884 – 23 December 1948) was a Japanese general who served as Prime Minister of Japan from 1941 to 1944 during the Second World War. His leadership was marked by widespread state violence and mass killings perpetrated in the name of Japanese nationalism.

Born in Tokyo to a military family, Tojo was educated at the Imperial Japanese Army Academy and began his career in the Imperial Japanese Army (IJA) in 1905. He served as a military attaché in Germany from 1919 to 1922, and rose through the ranks to become a general in 1934. In March 1937, he was promoted to chief of staff of the Kwantung Army whereby he led military operations against the Chinese in Inner Mongolia and the Chahar-Suiyan provinces. Later in 1938, Tojo was recalled to Tokyo to serve as vice-minister of the army. By July 1940, he was appointed minister of the army in the premiership of Fumimaro Konoe.

The Imperial Japanese Armed Forces (IJAF, full Japanese: 帝国陸海軍, romanized: Teikoku riku-kaigun or Nippon-gun (日本軍) for short, meaning "Japanese Forces") were the unified forces of the Empire of Japan. Formed during the Meiji Restoration in 1868, they were disbanded in 1945, shortly after Japan's defeat to the Allies of World War II; the revised Constitution of Japan, drafted during the Allied occupation of Japan, replaced the IJAF with the present-day Japan Self-Defense Forces.

The Imperial Japanese Army and the Imperial Japanese Navy functioned as the IJAF's primary service branches, with the country's aerial power being split between the Army Air Service under the former and the Navy Air Service under the latter.

The Imperial Japanese Navy land forces (大日本帝國海軍陸戦隊, Dai-Nippon Teikoku Kaigun Rikusentai) were a variety of land-based units of the Imperial Japanese Navy (IJN) organized for offensive operations, the defense of Japanese naval and shore-based facilities, military policing tasks, construction and engineering, training, and shore-based anti-aircraft roles; both overseas, and in the Japanese home islands. Units ranged from dedicated military police formations, to ad-hoc groups of naval personnel pressed into service as naval infantry, to professional marines, among others. The land forces were most active during the interwar period and World War II, with IJN land forces complementing, supporting, and in some cases, operating in-place of Imperial Japanese Army units. Upon Imperial Japan’s surrender, IJN land forces were disbanded alongside the IJN proper in 1945.

The Kwantung Army (Japanese: 関東軍, Kantō-gun) was a general army of the Imperial Japanese Army from 1919 to 1945.

The Kwantung Army was formed in 1906 as a security force for the Kwantung Leased Territory and South Manchurian Railway Zone after the Russo-Japanese War of 1904–1905 and expanded into an army group during the interwar period to support Japanese interests in China, Manchuria, and Mongolia. The Kwantung Army became the most prestigious command in the Imperial Japanese Army, and many of its personnel won promotions to high positions in the Japanese military and civil government, including Hideki Tojo and Seishirō Itagaki. The Kwantung Army was largely responsible for the establishment and proxy control of the Japanese puppet-state of Manchukuo in Manchuria and functioned as one of the main Japanese fighting forces during the 1937–1945 Second Sino-Japanese War.

The Mukden incident was a false flag event staged by Japanese military personnel as a pretext for the 1931 Japanese invasion of Manchuria.

On September 18, 1931, Lieutenant Suemori Kawamoto of the Independent Garrison Unit [ja] of the 29th Japanese Infantry Regiment [ja] detonated a small quantity of dynamite close to a railway line owned by Japan's South Manchuria Railway near Mukden (now Shenyang). The explosion was so weak that it failed to destroy the track, and a train passed over it minutes later. The Imperial Japanese Army accused Chinese dissidents of the act and responded with a full invasion that led to the occupation of Manchuria, in which Japan established its puppet state of Manchukuo five months later.

The First Sino-Japanese War (25 July 1894 – 17 April 1895), or the First China–Japan War, was a conflict between the Qing dynasty of China and the Empire of Japan primarily for influence over Korea. In Chinese it is commonly known as the Jiawu War. After more than six months of unbroken successes by Japanese land and naval forces and the loss of the ports of Lüshunkou (Port Arthur) and Weihaiwei, the Qing government sued for peace in February 1895 and signed the unequal Treaty of Shimonoseki two months later, ending the war.

In the late 19th century, Korea remained one of the Qing tributary states, while Japan viewed it as a target of imperial expansion. In June 1894, the Qing government, at the request of the Korean emperor Gojong, sent 2,800 troops to aid in suppressing the Donghak Peasant Revolution. The Japanese considered this a violation of the 1885 Convention of Tientsin, and sent an expeditionary force of 8,000 troops, which landed at Incheon. This army moved to Seoul, seized the Korean emperor, and set up a pro-Japanese government on 23 July 1894 in the occupation of Gyeongbokgung. The Qing government decided to withdraw its troops, but rejected recognition of the pro-Japanese government, which had granted the Imperial Japanese Army the right to expel the Qing's Huai Army from Korea. About 3,000 Qing troops still remained in Korea, and could be supplied only by sea; on 25 July, the Japanese Navy won the Battle of Pungdo and sank the steamer Kowshing, which was carrying 1,200 Qing reinforcements. A declaration of war followed on 1 August.