For as long as humans have existed, they have been in conflict. The earliest evidence of two different factions fighting one another to the death dates back at least 4,700 years, and there were likely many conflicts before that.

People go to war for many reasons. Independence, religion, territory, and political ideology have been some of the causes soldiers were willing to put their lives on the line for. Many have decided that money is worth going to war over. Mercenaries were common in ancient battles, and when the first recorded war ended, the victorious Sumerians “carried away as spoils the weapons of Elam.” As the world has progressed, war is still profitable. There are many companies earning billions from war to this day. These are 20 companies profiting the most from war.

Some wars are quick, especially for countries who spend a lot on their military. But this is not always the case. Before technology made it possible to kill many enemies from anywhere, opposing sides could retreat, take refuge in a fortified castle, and wait to go back out and fight. This allowed some wars in the past to drag out decades and even centuries.

24/7 Tempo has compiled a list of the longest wars in history by reviewing data and articles from various sources. In order to appear on this list, a conflict had to meet the definition of war as an open and usually declared armed conflict between political entities such as sovereign states or competing factions within the same state, such as a civil war. The conflict had to be sustained over a period of time and intended to resolve political or territorial disputes.

Click here to read about the longest wars in history