Province Wellesley to the British at the end of the 18th century. The Siamese nevertheless invaded Kedah in 1821, and it remained under Siamese control under the name of Syburi. In 1896, Kedah along with Perlis and Setul was combined into the Siamese province of Monthon Syburi which lasted until transferred to the British by the Anglo-Siamese Treaty of 1909. Incorporation into Malaya In World War II, Kedah (along with Kelantan) was the first part of Malaya to be invaded by Japan. The Japanese returned Kedah to their Thai allies who had it renamed Syburi, but it returned to British rule after the end of the war. Kedah became one of the states of the Federation of Malaya in 1948, which then achieved independence in 1957. Malaya was then enlarged to become Malaysia in 1963. Since 2017, the hereditary Sultan of Kedah has been Sultan Sallehuddin. The Kedah Sultanate began when the ninth Kedah Maharaja Derbar Raja or Phra Ong Mahawangsa, converted to Islam and changed his name to Sultan Mudzafar Shah I. Since then there have been 27 Sultans who ruled Kedah. On 11 May 2018, Mahathir Mohamad son Mukhriz Mahathir took his oath of office before Kedah Sultan Tunku Sallehuddin Ibni Almarhum Sultan Badlishah in a ceremony held in Istana Anak Bukit. Geography Kedah is the 8th largest state by land area and 8th most populated state in Malaysia, with a total land area of , and a population of 1,890,098. The Pedu Lake is the largest man-made lake in the state. Government Executive Kedah's Constitution was promulgated by its Ruler in July 1950. The various provisions laid down in the Constitution include the role and powers of the Monarch, the State Parliament and the State's Civil Service. The Sultan of Kedah is the constitutional ruler of the State. His position is hereditary and he holds office for life. The Ruler is the head of the religion of Islam in the State and the executive power of the state government is vested in him. The current Sultan is Sultan Sallehuddin ibni Almarhum Sultan Badlishah, who has reigned since 12 September 2017 after his elder brother Sultan Abdul Halim died on 11 September 2017. The State Executive Council, which along with the Sultan is Kedah's executive branch of government. It is composed of the Menteri Besar, who is its chairman and Kedah's head of government, and ten other members.