In their 1968 book The Lessons of History, Will and Ariel Durant wrote:

"In the last 3,421 years of recorded history only 268 have seen no war."

In all the other years, there was a war going on somewhere. Odds are, there were wars in isolated areas with little or no written history. I'd be surprised if there ever was a year where humans weren't fighting somewhere. In some years, there are literally dozens of wars underway somewhere. Often, they're relatively small affairs like the decades long insurgency in the Philippines. However, they're very real to the people caught up in the conflicts, like my wife's cousin who was killed in the PI last year.