In September 1939 New Zealand, along with the other Commonwealth nations, joined Britain in declaring war on Germany in response to the German invasion of Poland.
Despite a small population of only 1.63 million in 1940, an Expeditionary Force was quickly raised that became the 2nd New Zealand Division, seeing action in Greece, Crete, North Africa and finally ending the war in Italy. The division often fought with the support of British armour, but in September 1941 New Zealand began to form the 1st New Zealand Army Tank Brigade, to comprise three battalions of Valentine Infantry Tanks purchased from Britain. Before the Tank Brigade was complete however, on December 7th, 1941 the Japanese launched their surprise attack on Pearl Harbor, simultaneously declaring war on the British Empire and Commonwealth with attacks on Hong Kong and Malaya that brought the conflict much closer to home for New Zealand and Australia.