World War II was a global conflict that split the majority of the world's nations into two opposing military alliances: the Allies and the Axis powers. World War II is deemed to have begun in Europe in 1939 with the German invasion of Poland, resulting in the British and French declarations of war. The complexion of the war was changed completely in 1941 by the German invasion of the USSR in June and the Japanese attack on the USA in December. The Germans over-reached themselves in the USSR. In the Pacific the USA began to wrest back the initiative in mid 1942 and in campaigns steadily drove the Imperial Japanese back. In the west the USA first committed its forces in North-West Africa from November 1943, and then with the British and other allies in Italy from July 1943, and in northern and southern France during June and August 1944. From there the Allies drove back the Germans on the Western Front, securing total victory in May 1945. The USA devastated Japan, contributing to the ending of the war, by dropping atomic bombs on Hiroshima and Nagasaki in August 1945.