San Francisco International Airport (SFO) FAA Status: Advisory Due to RWY-TAXI / CONSTRUCTION, there is a Traffic Management Program in effect for traffic arriving San Francisco International Airport, San Francisco, CA (SFO). This is causing some arriving flights to be delayed an average of 47 minutes.
I'm fairly sure that I could get over a thousand wars in Europe in the last Millennia or so. So I'd say that there have probably been between 10,000 and 250,000 wars in human history. I'd expect a log distribution with very few wars with more than 100 million participants and a great many with fewer than a thousand.
American troops going to the battle line in the Forest of the Argonne, France, September 26, 1918. Courtesy of the Army Historical Foundation, NARA # 111-SC-22334 . In the 1900s, the United States fought in five wars. World War I was from 1914 to 1918. Many countries fought in this war. The United States entered the war in 1917.