In 1927, the country's pearling economy collapsed due to the introduction of Japanese cultured pearls in the world market. It is estimated that between 1929 and 1931, pearling entrepreneurs lost more than two-thirds of their income. Further aggravated by the Great Depression, many leading Bahraini businessmen, shopkeepers, and pearl-divers fell into debt. With the discovery of oil in 1932 and the subsequent production of oil exports in 1934, the country gained a greater significance in geopolitics. The security of oil supplies in the Middle East was a priority of the British, especially in the run-up to the Second World War. The discovery of oil led to gradual employment of bankrupt divers from the pearling industry in the 1930s, eventually causing the pearling industry to disappear. During the war, the country served as a strategic airbase between Britain and India as well as hosting RAF Muharraq and a naval base in Juffair. Bahrain was bombed by the Italian Air Force in 1940. In 1947, following the end of the war and subsequent Indian independence, the British residency of the Persian Gulf moved to Manama from Bushire.