In 1943, during World War II, the Portuguese ruler António de Oliveira Salazar leased air and naval bases in the Azores to Great Britain. The occupation of these facilities in October 1943 was codenamed "Operation Alacrity" by the British. This was a key turning point in the Battle of the Atlantic, enabling the Royal Air Force, the U.S. Army Air Forces, and the U.S. Navy to provide aerial coverage in the Mid-Atlantic gap. This helped them to protect convoys and to hunt hostile German U-boats. In 1944, the U.S. constructed a small and short-lived air base on the island of Santa Maria. In 1945, a new base was constructed on the island of Terceira, named Lajes Field. This air base is in an area called Lajes, a broad, flat sea terrace that had been a large farm. Lajes Field is a plateau rising out of the sea on the northeast corner of the island. This air base is a joint American and Portuguese venture. Lajes Field continues to support the American and Portuguese Armed Forces.