Sweden

As to length of time without war, probably Paul Cortez is correct: the 31 years between the War of 1812–1815 and the Mexican-American War of 1846–48. Short answer is that Our Nation averages a good armed conflict approximately every 25 years.

So here, the US are said to be at war in 1775, 1776, 1777, 1778, 1779, 1780, 1781, 1782, 1783. …

In addition to that, most countries which remain outside are tied to the EU by economic agreements and treaties such as the European Economic Area. Within the zone of integration, there has been no conflict since 1945, making it the longest period of peace on the western European mainland since Pax Romana.

if you take the US for example, since its inception in 1776 it has only had 18 peaceful years and the longest stretch was 5 years 1935–1940 because quite frankly you couldn’t afford a war due to the great depression and the policy of isolationism.

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 long peace began after WWII and has held for more than 70 years. Political scientists argue that various 20th century developments reduced the risk of global conflicts during this period.

Nuclear weapons have helped maintain peace between the great powers and have not led their few other possessors into military adventures. Their further spread, however, causes widespread fear.