The Cold War era which lasted for around 45 years collapsed in 1990-1991 as the result of the following events;
1. Gulf crisis and Gulf war proved the supremacy of US-led coalition against Iraq. The UN Security Council passed several resolutions against Iraq without any resistance from Moscow or Beijing.
2. The dismantling of Warsaw Pact and Soviet disunion. The collapse of communist rule in the former USSR & the subsequent emergency of 15 sovereign states (six Muslim & nine non-Muslim) also encouraged the United States to assert its position on several issues.
3. Nuclear Proliferation, particularly in some developing countries.
4. Action against Libya.
5. Seeking economic concessions from Japan & West European countries to over its economic problem. The cold war ended in 1990.