Although the Empire of Japan was already at war with the Republic of China in 1937, the world war is generally said to have begun on 1 September 1939, with the invasion of Poland by Germany, and subsequent declarations of war on Germany by France and most of the countries of the British Empire and Commonwealth. Germany set out to establish a large empire in Europe. From late 1939 to early 1941, in a series of campaigns andtreaties, Germany conquered or subdued much of continental Europe. Following the Molotov–Ribbentrop Pact, the nominally neutral Soviet Union fully or partially invaded, occupied and annexed territories of its six European neighbours, including Poland. The United Kingdom and its Commonwealth remained the only major force continuing the fight against the Axis, with battles taking place in North Africa as well as the long-running Battle of the Atlantic. In June 1941, the European Axis launched an invasion of the Soviet Union, giving a start to the largest land theatre of war in history, which tied down the major part of the Axis' military forces for the rest of the war. In December 1941, the Empire of Japan, which aimed to dominate East Asia and Indochina, joined the Axis, attacked the United States and European territories in the Pacific Ocean, and quickly conquered much of the West Pacific.