Editing Second World War (section)

== War breaks out in Europe ==
Germany invaded Poland on 1 September 1939. The German attack used armoured movement, air attack, and coordinated ground operations to break Polish defences. The Soviet Union invaded eastern Poland on 17 September 1939. Warsaw surrendered on 27 September 1939, and the last major Polish field forces surrendered on 6 October 1939.<ref name="ushmm-key-dates" />

After Poland, western Europe entered the Phoney War. Britain and France remained at war with Germany, but there was little major land fighting on the western front. At sea, the Battle of the Atlantic began as German submarines and surface raiders attacked Allied shipping.

The Soviet Union attacked Finland on 30 November 1939. The Winter War ended on 13 March 1940 with Finnish territorial losses. In 1940, the Soviet Union occupied Estonia, Latvia, and Lithuania and took territory from Romania.