The United States later participated in World War II, becoming a global power after it helped to secure victory for the allies in 1945; its vast economic and military resources including a short-lived period of monopoly on nuclear weapons made the U.S. one of the world's three remaining superpowers along with the USSR and the British Empire. After the deconstruction of the British Empire in the latter half of the 20th century (a process termed decolonization), the United States vied against the Soviet Union as one of the two remaining superpowers in the world in the Cold War. Upon the collapse of the Soviet Union in 1991, it became the sole superpower in the world, sometimes referred to as a hyperpower.