"Long Peace" is a term for the unprecedented historical period following the end of World War II in 1945 to the present day. The period of the Cold War (1945–1991) was marked by the absence of major wars between the great powers of the period, the United States and the USSR. First recognized in 1986, such a period of "relative peace" between major powers has not been documented in human history since the Roman Empire.
In the 1990s, it was thought that the Long Peace was a unique result of the Cold War. However, when the Cold War ended the same trends continued in what has also been called the "New Peace". This period has exhibited more than a quarter of a century of even greater stability and peacefulness, and has also shown continued improvements in related measurements such as the number of coups, the amount of repression, and the durability of peace settlements. Though civil wars and lesser military conflicts have occurred, there has been a continued absence of direct conflict between any of the largest GDP economies; instead, wealthier countries have fought limited small-scale regional conflicts with poorer countries. Conflicts involving smaller economies have also gradually tapered off. Overall, the number of international wars decreased from a rate of six per year in the 1950s to one per year in the 2000s, and the number of fatalities decreased from 240 reported deaths per million to less than 10 reported deaths per million.
Major factors cited as reasons for the Long Peace have included the deterrence effect of nuclear weapons, the economic incentives towards cooperation caused by globalization and international trade, the worldwide increase in the number of democracies, the World Bank's efforts in reduction of poverty, and the effects of the empowerment of women and peacekeeping by the United Nations. However, none of these are sufficient explanations on their own, so additional or combined factors are likely. Other proposed explanations have included the proliferation of human rights, increasing education and quality of life, changes in the way that people view conflicts (such as the presumption that wars of aggression are unjustified), the success of non-violent action, and demographic factors such as the reduction in birthrates.
In the book The Better Angels of Our Nature, Steven Pinker says that this is part of a trend that has continued since the beginning of recorded history, and other experts have made similar arguments. While there is general agreement among experts that we are in a Long Peace and that wars have declined since the 1950s, Pinker's broader thesis has been contested. Critics have also said that we need a longer period of relative peace in order to be certain, or have emphasized minor reversals in specific trends, such as the increase in battle deaths between 2011 and 2014 due to the Syrian Civil War. While Pinker's work has received some publicity, most information about the Long Peace and related trends remains outside public awareness, and some data demonstrates a widespread misperception that the world has become more dangerous.
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