the beginning of the Portuguese Restoration War, not by the professional military, who were occupied with warfare on the Portuguese mainland, but by local people attacking a fortified Castilian garrison. Overpopulation and emigration In the late 16th century, the Azores and Madeira began to face problems of overpopulation. Responding to the consequent economic problems, some people of the Azores began to emigrate to Brazil. Liberal Wars of 1828–1834 The Portuguese Civil War (1828–1834) had strong repercussions in the Azores. In 1829, in Praia da Vitória, the liberals won over the absolutists, making Terceira Island the main headquarters of the new Portuguese regime and also where the Council of Regency () of Maria II of Portugal was established. Beginning in 1868, Portugal issued its stamps overprinted with "" for use in the islands. Between 1892 and 1906, it also issued separate stamps for the three administrative districts of the time. Arbitrary district divisions 1836–1976 From 1836 to 1976, the archipelago was divided into three districts, equivalent (except in area) to those in the Portuguese mainland. The division was arbitrary and did not follow the natural island groups, rather reflecting the location of each district capital on the three main cities (none of which were on the western group). Angra do Heroísmo consisted of Terceira, São Jorge, and Graciosa, with the capital at Angra do Heroísmo on Terceira. Horta consisted of Pico, Faial, Flores, and Corvo, with the capital at Horta on Faial. Ponta Delgada consisted of São Miguel and Santa Maria, with the capital at Ponta Delgada on São Miguel. Modern period In 1931, the Azores (together with Madeira and Portuguese Guinea) revolted against the Ditadura Nacional and were held briefly by rebel military. 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.