Portugal during World War II
Upon the start of World War II in 1939, the Portuguese Government announced on 1 September that the 600-year-old Anglo-Portuguese Alliance remained intact, but that since the British did not seek Portuguese assistance, Portugal was free to remain neutral in the war and would do so. In an aide-mémoire of 5 September 1939, the British Government confirmed the understanding. As Hitler's occupation swept across Europe, neutral Portugal became one of the Continent's last escape routes. Portugal managed to remain neutral throughout the war despite extraordinary pressures from both sides, notably over the strategically located Azores islands and over the wolfram (tungsten) trade.
World War II by country
Following the Nazi invasion of the Soviet Union, which cut off their supply of tungsten metal, Germany sought tungsten from Portugal. Salazar attempted to limit their purchases, and in late 1941, German U-boats attacked Portuguese ships. In January 1942 Salazar signed an agreement to sell tungsten to Germany. In June 1943, Britain invoked the long-standing Anglo-Portuguese Alliance requesting the use of the Azores, to establish an air force and naval air base. Salazar complied at once. The Allies promised all possible aid in the event of a German attack and guaranteed the integrity of Portugal's territorial possessions. In 1944, Portugal declared a total embargo of tungsten shipments to Germany. Germany protested but did not retaliate.