What is the most common early military strategy?
A popular military tactic to use early in the game is called the “swordsmen rush”, or “sword rush”. Because the best attacker in the Ancient Age is a swordsman with an attack of 3, and the best defender (spearman) only has 2 defense, many people choose to found a couple early cities, and quickly build barracks in them. Then, they will amass a sizeable force of swordsmen, and use that to declare war on their neighbors before they can build up their defense. Of course, this strategy require the civilization has access to Iron needed to build swordsmen, but if they do, this tactic can gain them a lot of early land and hurt the AI for the rest of the game. Variations of this strategy also include using just horsemen if you have no Iron, or a combination of swordsmen/horsemen/catapults for a more varied approach against the AI. Also, view this article that deals with this strategy too.