The Long Peace means there have been no wars between major powers since 1945, we fear nuclear weapons. All wars now engaged in by great powers are asymmetric.
https://en.wikipedia.org/wiki/Long_Peace
also see http://www.fallen.io/ and https://www.dancarlin.com/hardcore-history-59-the-destroyer-...
Edit: second longest, but still > 16 years. We'll break the record soon enough.