The Empire of Japan (大日本帝国; Dai Nippon Teikoku) was the official title of Japan before the end of World War II. The names Imperial Japan and Japanese Empire are also used.
The empire had the Meiji Constitution (1889) which states the Japanese Emperor is the head of state and has sovereignty over the nation.
Yoshinobu Tokugawa, the 15th Shogun of the Tokugawa Shogunate, returned power to the Emperor with "The Return of Sovereignty" (大政奉還; Taisei Hōkan), afterwhich the Imperial Court declared The Restoration of the Monarchy" (王政復古; Ōsei Fukko). With this, the feudal anti-shogunate clans, Satsuma and Chōshū, formed the base of the new Meiji-government and with the intentions of becoming an empire the country was renamed to The Grand Imperial Nation of Japan.
The country was formally known as The Grand Imperial Nation of Japan in accordance to The Constitution of the Grand Imperial Nation of Japan (大日本帝国憲法 Dai Nippon Teikoku Kenpou). However Japan (日本 Nihon）, Great Japan (大日本 Dai Nippon), The Great Nation of Japan (大日本国 Dai Nippon Koku), The Empire of Japan (日本帝国 Nippon Teikoku) were misused, and it was not until 1936 that the proper title of the country was standardized.
In 1946, the year after the close of the war, Japan restructured as part of their defeat, and the country's title was revised to The Country of Japan (日本国 Nihon Koku).
With the Great Depression, Japan, like some other countries, turned to Fascism. While it was a unique form of the system, probably due to cultural differences, Japan parallelled the western form very closely, as its Feudalism did hundreds of years earlier. Unlike Adolf Hitler and Benito Mussolini, though, Japan had two economic goals in developing an empire.
First, as with its European counterparts, a tightly-controlled domestic military industry apparently jump started the nation's economy in the midst of the depression. Also, due to the lack of resources on Japan's home islands, in order to maintain a strong industrial sector with strong growth, raw materials such as iron, oil, and coal largely had to be imported. Most of these materials came from the United States. So, for the sake of the military-industrial development scheme, and industrial growth on the whole, mercantilist theories prevailed, and the Japanese felt that resource-rich colonies were needed to compete with European powers. Korea (1910) and Formosa (Taiwan, 1895) had earlier been annexed as primarily agricultural colonies. Manchuria's iron and coal, Indochina's rubber, and China's vast resources were prime targets for industry.
Manchuria was invaded and successfully conquered in 1931, with little trouble. Ostensibly, Japan did this to liberate the Manchus from the Chinese, just as the annexation of Korea was supposedly an act of protection. As with Korea, a puppet government (Manchukuo) was installed. Jehol, a Chinese territory bordering Manchuria, was taken in 1933.
Japan invaded China in 1937, creating what was essentially a three-way war between Japan, Mao Zedong's communists, and Chiang Kai-shek's nationalists. Japan took control of much China's coasts and port cities, but very carefully avoided European spheres of influence. In 1936 before the Chinese invasion, Japan signed an anti-communism treaty with Germany, and another with Italy in 1937.
Timeline of Japanese Expansionism
1926: Emperor Taisho dies (December 25).
1927: Tanaka Giichi becomes prime minister (April 20).
1928: Hirohito is formally installed as emperor (November 10).
1929: Hamaguchi Osachi becomes prime minister (July 2).
1930: Hamaguchi is wounded in an assassination attempt (November 14).
1931: Hamaguchi dies and Wakatsuki Reijiro becomes prime minister (April 14). The Sino-Japanese War starts with the Mukden Incident (September 18). Inukai Tsuyoshi becomes prime minister (December 13) and increases funding for the military in China.
1932: After an attack on Japanese monks in Shanghai (January 18), Japanese forces shell the city (January 29). Manchukuo is established with Henry Pu Yi as emperor (February 29). Inukai is assassinated during a coup attempt and Saito Makoto becomes prime minister (May 15). Japan is censured by the League of Nations (December 7).
1933: Japan leaves the League of Nations (March 27).
1934: Okada Keisuke becomes prime minister (July 8). Japan withdraws from the Washington Naval Treaty (December 29).
1936: Coup attempt (February 26 Incident). Hirota Koki becomes prime minister (March 9). Japan signs its first pact with Germany (November 25) and occupies Tsingtao (December 3). Mengchiang established in Inner Mongolia.
1937: Hayashi Senjuro becomes prime minister (February 2). Prince Konoe Fumimaro becomes prime minister (June 4). Battle of Lugou Bridge (July 7). Japan captures Beijing (July 31). Japanese troops occupy Nanjing (December 13), beginning the Nanjing massacre.
1938: Battle of Taierzhuang (March 24). Canton falls to Japanese forces (October 21).
1939: Hiranuma Kiichiro becomes prime minister (January 5). Abe Nobuyuki becomes prime minister (August 30).
1940: Yonai Mitsumasa becomes prime minister (January 16). Konoe becomes prime minister for a second term (July 22). Hundred Regiments Offensive (August-September). Japan occupies Indochina in the wake of the fall of Paris, and signs the Tripartite Pact (September 27).
1941: General Tojo Hideki becomes prime minister (October 18). Japanese naval forces attack Pearl Harbor, Hawaii (December 7), prompting the United States to declare war on Japan (December 8). Japan conquers Hong Kong (December 25).
1942: Singapore surrenders to Japan (February 15). Japan bombs Australia (February 19). Doolittle Raid on Tokyo (April 18). Battle of the Coral Sea (May 4 - 8). American forces in the Philippines surrender (May 8). Japan defeated at the Battle of Midway (June 6).
1943: U.S. victory in Battle of Guadalcanal (February 9). Japan defeated at Battle of Tarawa (November 23).
1944: Tojo resigns and Koiso Kuniaki becomes prime minister (July 22).
1945: U.S. bombers begin firebombing of major Japanese cities. Japan defeated at Battle of Iwo Jima (March 26). Admiral Suzuki Kantaro becomes prime minister (April 7). Japan defeated at Battle of Okinawa (June 21). U.S. drops atomic bombs on Hiroshima (August 6) and Nagasaki (August 9). Japan surrenders (August 14): Allied occupation begins.