Spearfighters are the very first military unit in the game. A player will rely on it for quite a while because they are versatile and cheap. Spearfighters are trained in a Spearfighter Barracks, which is unlocked after researching the Spears technology. Unlike other units, it takes only a few seconds to be trained. Spearfighters have a defense bonus when standing in bushes and forest terrain. Their effectiveness against fast unit makes them very useful. Also, they have the highest attack after the horseman in Bronze Age and also the highest mobility. The player only needs to be careful as Spearfighters are easily defeated by Heavy Class units. Combine them with Slingers to eliminate Warriors before having close combat with it. Succeeded by the Soldier in the Iron Age.
Two spear fighters are the default city defense if not specified otherwise. Furthermore the spear fighter with its short recruitment time and the low training cost is great as a "trash unit". So if a quest tells you to delete units normally the spear fighters are the go to, if you don't want to loose any valuable units. This is very helpful in special events.