I will go straight to the facts. The longest recorded war in the history of mankind is World War 2. It started in September of 1939 to 1945
Some people think that the cold war was the longest since it last from around 1947-1991. However, they must realized that the cold war was the name of the tension between the U.S and its allies and the Soviet Union and its allies (Warsaw Pact). It essentially was a series of conflicts and indirect smaller wars, not one long war.
