There are several factors of the end of the Cold War. The economies of the Soviet Union and of the Easten Bloc had become stagnated and technologically backward. The subsequent worsening of living standards and the aggravation of longtime, unsolved social issues made the situation even more complicated. The perestroika and the glasnost initiated by Soviet secretary-general Mikhail Gorbachev intented to promote social, political and economic reforms but they did not succeed; they brought instead instability and protests in the Soviet republics. Besides, the election of Ronald Reagan as US president put additional pressure on the USSR. Reagan promoted systems of new weapons and an ambitious space program that could not have been matched by Moscow. This combination of economic, social and diplomatic factors led to the end of the Cold War.
After the end of the Cold War, the US became the only superpower. With confidence after what it saw as its "victory" in the Cold War, American foreign policy became more unilateral.
313 AD, the Emperor Constantine issued the Edict of Milan, which accepted Christianity: 10 years later, it had become the official religion of the Roman Empire.
