"The three-round Communist struggle for Greece began in 1941, against a background of conflicting Communist doctrine, shifting foreign alliances, territorial disputes, and key personality differences. During the German occupation of Greece (1941-1944), the National Liberation Front attempted to regain control of the country and overthrow the monarchy. In 1944, when the Communists sought to seize power after the German occupation, they were frustrated by the intervention of British forces. After 1946, the most protracted part of the struggle, U.S. forces replaced the retiring British, the United Nations sent fact-finding missions, and conventional warfare shifted to guerrilla tactics.".