Japanese forces launch a surprise attack against Russian-controlled Port Arthur, marking the start of the Russo-Japanese war.

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 1910 to 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.

The Battle of Port Arthur of 8–9 February 1904 marked the commencement of the Russo-Japanese War. It began with a surprise night attack by a squadron of Japanese destroyers on the neutral Russian fleet anchored at Port Arthur, Manchuria, and continued with an engagement the following morning; further skirmishing off Port Arthur would continue until May 1904. The attack ended inconclusively.

The Russian Empire was an empire that spanned most of northern Eurasia from its establishment in November 1721 until the proclamation of the Russian Republic in September 1917. At its height in the late 19th century, it covered about 22,800,000 km² (8,800,000 sq mi), roughly one-sixth of the world's landmass, making it the third-largest empire in history, behind only the British and Mongol empires. It also colonized Alaska between 1799 and 1867. The empire's 1897 census, the only one it conducted, found a population of 125.6 million with considerable ethnic, linguistic, religious, and socioeconomic diversity.