Neutral powers during World War II

The neutral powers were countries that remained neutral during World War II. Some of these countries had large colonies abroad or had great economic power. Spain had just been through its civil war, which ended on 1 April 1939 (five months prior to the invasion of Poland)—a war that involved several countries that subsequently participated in World War II.

During World War II, the neutral powers took no official side, hoping to avoid attack. However, Portugal, Sweden, and Switzerland all helped the Allies by supplying "voluntary" brigades^[1] to the United Kingdom,^[2] while Spain avoided the Allies in favor of the Axis, supplying them with its own voluntary brigade, the Blue Division. Ireland generally favoured the Allied side, as with the United States. The United States remained officially neutral until 8 December 1941, a day following the attack by Japan on Pearl Harbor.

The Lateran Treaty between Italy and the Holy See, signed in 1929, required that the Pope maintain "perpetual neutrality in international relations". Accordingly, Vatican City was officially neutral throughout the war.

Several countries suffered invasions despite their efforts to be neutral. These included Nazi Germany's invasion of Denmark and Norway on 9 April 1940—then Belgium, the Netherlands, and Luxembourg on 10 May 1940. On the same day, 10 May 1940, the British, having already invaded the Faroe Islands in April, invaded Iceland and established an occupying force (subsequently replaced by the then-neutral United States). The Soviet Union invaded Lithuania on 15 June 1940 and Latvia and Estonia on 17 June. In the Balkans, the Italo-Greek War began on 28 October 1940 and Yugoslavia was invaded in April 1941. Iran was also attacked and occupied by Britain and the Soviet Union in August 1941 and later declared war on Nazi Germany.

See also the histories of Afghanistan, Andorra, Guatemala, Liechtenstein, Saudi Arabia and Yemen during this period.