New Zealand was one of the first countries to become involved in the global conflict precipitated by Germany's invasion of Poland on 1 September 1939. Its 2176-day involvement, encompassing all but three days of the period now accepted as the Second World War, was matched only by Great Britain, Australia, and British colonial possessions.
In contrast to its entry to the First World War, New Zealand acted in its own right by formally declaring war on Germany on 3 September (unlike Australia, which held that the King's declaration, as in 1914, extended to all his Dominions). From time to time it is suggested, somewhat disingenuously, that New Zealand entered the war even before Britain because its time zone in September 1939 was ten and a half hours ahead of British Summer Time. In fact, New Zealand acted only after formal advice was received of the expiry of the British government's ultimatum to Germany to withdraw from Poland, shortly before midnight on 3 September (New Zealand time). The state of war between New Zealand and Germany was held to have existed from the expiry of the ultimatum - in short, the same moment that war began between Britain and Germany (9.30 p.m., 3 September, New Zealand time).
For most New Zealanders, association with Britain in its time of crisis was both natural and necessary. As a firm opponent of appeasement, New Zealand had long advocated a strong stance against the fascist dictatorships. Economic considerations alone ensured that a threat to Britain was seen as a threat to New Zealand - as in 1914.
Given New Zealand's reliance on British power for security, and the lack of alternatives, defensive self-interest was another strong motivator towards involvement. Underlying both economic and defence aspects was a sentimental link that made support for the 'kith and kin' in Britain as natural as it was inevitable. Only one political party opposed New Zealand's participation in the war - the small Communist Party, faithful to the false promise of the Nazi-Soviet Non-Aggression Pact of 23 August 1939.
In the fifty years after the war no significant academic critique of New Zealand's stance appeared, though an undercurrent of criticism can be discerned in suggestions, sometimes advanced in newspaper editorials, that New Zealand sent troops to fight in Britain's war. A failure to recognise either strategic imperatives or the close ties of self-interest as well as sentimental loyalty that bound New Zealand with Britain usually lie behind such pronouncements.