Montevideo, founded by the Spanish in 1726 as a military stronghold, soon took advantage of its natural harbor to became an important commercial center. Annexed by Brazil as a separate province in 1821, Uruguay declared its independence four years later and secured its freedom in 1828 after a three-year struggle. The administrations of President BATLLE in the early 20th century established widespread political, social, and economic reforms. A violent Marxist urban guerrilla movement named the Tupamaros, launched in the late 1960s, led Uruguay's president to agree to military control of his administration in 1973. By yearend, the rebels had been crushed, but the military continued to expand its hold throughout the government. Civilian rule was not restored until 1985. Uruguay's political and labor conditions are among the freest on the continent.