Infantry is the branch of an army dedicating to fighting on foot. It is the oldest military branch in history, existing from the first of armies to the present day. From simply throwing stones at the enemy to wielding versatile assault rifles to combat enemy Machine Gun fire, infantry has seen the evolution of human combat from the very beginning, and Rise of Nations reflects on this. Infantry units are created at the the Barracks, the only recruitment building avaliable from the Ancient Age onwards, as soon as Military 1 (The Art Of War) is researched. Unlike other unit classes, most Infantry units at full health consist of three soldiers each, the number decreasing with the unit's hit points. This effect is not only cosmetic, however. The larger size provides a considerable advantage in rate of fire over smaller units, and allows an infantry army to cover more terrain, making easier to trap, contain, or surround an enemy. On the other hand, this also makes infantry units more vulnerable targets, as individual members of the unit are more easily incapacitated. For instance, Attrition damage affecting a single soldier damages the rest of its unit nontheless, and a sucessful Cavalry charge against an infantry line will dispatch many of its men right away, and may cut with the infantry's advantage in numbers.
With their protagonism throughout history in all sorts of roles and equipment, Infantry is the unit class with the greatest variety of units and unit types in Rise of Nations. Infantry types are the following:
Avaliable in the Ancient Age. Fast and cheap, Light infantry specialize in dealing with enemy Foot Archers, as they do the most damage towards them. Though their range and/or speed allows them to stay away from Heavy Infantry, which they are weak against, it does not suffice against Light or Heavy Cavalry, which will easily wipe them out. From the Gunpowder Age onwards, Light Infantry becomes Gunpowder Infantry.
Avaliable in the Ancient Age. Foot Archers are particularly adept at countering Heavy Infantry and Horse Archers, but Light Cavalry and Infantry will make quick work of them, as does Heavy Cavalry, if its slower speed doesn't refrain it from reaching the archer lines. From the Enlightenment Age onwards, Foot Archers become Gunpowder Infantry.
Avaliable in the Ancient Age. The slowest but strongest of infantry types. Very effective in melee, its strengths is seen against both Light and Heavy Cavalry, which they can dispatch quickly; any early army would be in serious trouble facing cavalry without them. Likewise, Light Infantry is at a serious disadvantage, as long as the heavy infantrymen can reach them. Heavy Infantry is also the most efective infantry type against buildings, with an attack bonus against them and more resistance to their projectiles, making them the most solid choice for capturing cities. However, they are very vulnerable to Foot Archers, Ranged Cavalry, Gunpowder Infantry, and Elephants. From the Industrial Age onwards, Heavy Infantry employs anti-tank weaponry, becoming the counter to Tanks that they were to the preceding Melee Cavalry.
Avaliable in the Gunpowder Age. Strong against Heavy Infantry and Ranged Cavalry, Weak against Light and Heavy Cavalry. From the Industrial Age onwards, Gunpowder Infantry upgrades to Modern Infantry.