Answer:
World War II began with the invasion of Poland by Germany.
Explanation:
The German invasion of Poland on 1 September 1939 was the initial event of World War II. It became politically possible after the conclusion of the Molotov-Ribbentrop Agreement between Germany and the Soviet Union on August 23, 1939. The agreement guaranteed Germany the neutrality of the Soviet Union in the event of a German attack on Poland. The Soviet Union, for its part, invaded Poland on September 17, 1939 and occupied its eastern parts.
Poland, with its large army, had believed that it would be able to cope with the German invasion at first, largely by itself, until Britain and France were able to help. Technically and tactically, however, the Polish armed forces proved outdated compared to the German army. France would have been able to attack the Siegfried line, but it had confined itself to making only one attack on the Saarland with a ban on advancing near the Siegfried line. Thus, France did not actually relieve the pressure on Poland, but allowed Germany to continue its effective offensive in Poland. Britain, on the other hand, did not have a significant number of ground forces to send to Poland, so in practice Poland had to fight alone despite the British and French security guarantees and declarations of war.
