New Zealand declared war on Germany, following the lead of Great Britain in 1939

New Zealand was very loyal to the British and not only declared war with the British, but expected New Zealand men to serve under British command. New Zealand declared war on Germany at the same time the British did, on the expiration of their ultimatum. In 1940, in North Africa, the Long Range Desert Group was formed with New Zealand and Rhodesian soldiers. Actually, both New Zealand men and women served in the war. They fought in both the European theater and the far east.
In 1939, New Zealand seems to have had a very conservative outlook. They took a strong stand opposing the Fascist dictators. That seems very unlike the present, where New Zealand has a very progressive government.
New Zealand sent an expeditionary force to Europe to help the British. When Italy entered the war, the New Zealand government formed a War Cabinet of both the Government and the Opposition. They also opened diplomatic relations with the United States, and then in 1944, with the Soviet Union. Late in the War, New Zealand decided to become involved with the United Nations.
Oddly enough, the government at the start of the war was Labour, but they instituted all sorts of strict measures. They started censorship, they jailed "enemy aliens" and New Zealand Pacifists. A methodist minister was jailed for 2-1/2 years for publishing a "Christian pacifist bulliten". This is based on the New Zealand Official History.