major social reform between 1926 and 1957, under the de facto rule of Charles Belgrave, the British advisor to Shaikh Hamad ibn Isa Al-Khalifa (1872-1942). The country's first modern school was established in 1919, with the opening of the Al-Hiddaya Boys School, while the Persian Gulf's first girls school opened in 1928. The American Mission Hospital, established by the Dutch Reform Church, began work in 1903. Other reforms include the abolition of slavery, while the pearl diving industry developed at a rapid pace. These reforms were often vigorously opposed by powerful groups within Bahrain including sections within the ruling family and merchants. In order to counter conservatives, the British removed the Ruler, Isa ibn Ali Al Khalifa in 1923 and replaced him with his son. Some Sunni families left Bahrain to mainland Arabia, whilst clerical opponents of social reforms were exiled to Saudi Arabia and Iran. The heads of some merchant and notable families were likewise exiled. Britain's interest in Bahrain's development was motivated by concerns over the ambitions of the Saudi-Wahabi and the Iranians. Discovery of oil The discovery of oil in 1932 by Bahrain Petroleum Company brought rapid modernisation to Bahrain. Relations with the United Kingdom became closer, as evidenced by the British Royal Navy moving its entire Middle Eastern command from Bushehr in Iran to Bahrain in 1935. British influence continued to grow as the country developed, culminating with the appointment of Charles Belgrave as advisor. He went on to establish a modern education system in Bahrain. Bahrain participated in the Second World War on the Allied side, joining on 10 September 1939. On 19 October 1940, four Italian SM.82s bombers bombed Bahrain alongside Dhahran oilfields in Saudi Arabia, targeting Allied-operated oil refineries. Although minimal damage was caused in both locations, the attack forced the Allies to upgrade Bahrain's defences which further stretched Allied military resources. After World War II, increasing anti-British sentiment spread throughout the Arab World and led to riots in Bahrain. The riots focused on the Jewish community, which included distinguished writers, singers, accountants, engineers and middle managers working for the oil company, textile merchants with business all over the peninsula, and free professionals. The leftist movement The National Union Committee (NUC), a leftist nationalist movement associated with the labour unions, was formed in 1954 calling for the end of British interference and political reforms. Work sites were plagued with frequent strikes and occasional