the usa was be far the richest and most powerful nation in the world. however relation between the usa and the soviet union quickly cooled after 1945. by 1947 the cold war had begun. in 1946 the british were helping the greek government fight communist guerrillas. however british was exhausted after world war II and could not continue. on 12 march 1947 truman announced that usa must 'support free people who are resisting attempted subjugation by armed minorities or by outside pressures .