The earliest significant settlements in the UAE appeared in the Bronze Age. They were near modern Abu Dhabi. The next major groups were the Persians and the Greeks. In Middle Ages this territory was controlled by the Kingdom of Hormuz, later the Portuguese arrived. The ancestors of the rulers of four of the seven emirates that today make up the UAE were the Qawassim and the Bani Yas. In 1820 the British imposed a General Treaty of Peace on nine Arab sheikhdoms. Saudi Aravia had the intentions to conquest the area, but the British protected the federation. In 1951 the Trucial States Council was formed. On 2 December 1971 six of the emirates united and as a result the new country came into existence. The following year one more emirate joined the federation. It was Ras al-Khaimah. Nowadays, the UAE remains the only united Arab country in the region. The considerable prosperity of the UAE after a hard period of stagnation and poverty was reached because of the development of the oil and gas industries. Tourism plays one of the main roles in the country’s economy.