Uganda is sometimes called the "land of lakes," because almost one-third of its territory is covered by water. The greatest Ugandan body of water is Lake Victoria, the second-largest freshwater lake in the world. The world's longest river, the Nile, also has its source in Uganda. Uganda has faced a great deal of turmoil since becoming independent in 1962. During the rule of Idi Amin in the 1970s, some 300,000 Ugandans—mostly from the Acholi and Lano tribes—were massacred. Political instability and unrest in the country continued into the next decade. However, since the 1986 election of Yoweri Museveni, Uganda has made great progress socially and economically. In recent years the country has forged closer ties with the United States and other foreign nations.