Light Infantry are skirmisher units in Empire: Total War.
Light infantry are skirmishers who harass the enemy while screening the main body of an army.
Initiative, aggression and pace of action mark these men out and they consider themselves a cut above other infantry, regardless of the title that they use. Light infantry, jaegers or chasseurs do not mindlessly follow orders, but pick and choose their own ground and targets, using such cover as they can find. They carry standard smoothbore, muzzle-loading muskets, but they do not rely on massed volley fire: they deliberately aim (as well as they can, given that muskets lack sights), at individuals within the enemy ranks. The selective fire can disrupt enemy formations or drive off enemy skirmishers. Over time, developments in tactics and weapons will make them very effective as snipers as well as covering forces.
In 1700, many European nations did not recruit light infantry regiments. Each line infantry regiment had a light company, but the mass volley was the proper way to employ firepower. As irregular light troops proved their worth and tribal natives refused to co-operate by fighting formal, set piece battles, it was realised that collecting together light companies in ad hoc regiments was no longer enough. Direct recruitment of light infantry regiments began in earnest, and by the end of the 18th Century every army fielded fast, light regiments.
Light Infantry are skirmishers, screening the rest of the army from harassment. Light Infantry have a slightly greater range than Line Infantry. They become invisible to the enemy when immobile and at a sufficient distance, or when in tall grass or woods. They also all fire at once, giving them a firepower advantage against Line Infantry regiments before the Fire by Rank technology is researched. Their Light Infantry Behavior option makes them spread out and crouch, making them less susceptible to fire while allowing them to stand in front of other Infantry and fire without worrying about friendly fire. Although they have less range than their late-game Riflemen counterparts, Light Infantry reload far more quickly as they use muskets instead of rifles, allowing them to remain competitive.
When utilizing light infantry behavior doctrine, these units crouch while stationary. Putting crouching regiments directly in front of line infantry can allow both line and light infantry to shoot without fear of friendly fire due to the lower profile of the light infantry.
Light Infantry have their weaknesses. They have half the numbers of regular Line Infantry (which means that they can only deliver half the effective firepower in later stages), much lower morale, and next to no melee capability. Therefore, Light Infantry should avoid in a melee engagement at all costs, and direct firefights with line infantry if possible. Light infantry also run out of ammunition quite quickly.
Light infantry's range advantage allows them to pick off advancing enemy forces. Therefore, wise officers often use them on the flanks or as a screen in front of their army, wearing down enemy units until the line infantry can begin firing.
In addition to their muskets, light infantry can also deploy wooden stakes. These stakes can be used to deny crucial chokepoints, such as bridges and river crossings to enemy horsemen. And, if serving in an army which has not moved for two turns on the campaign map, light infantry are able to deploy Fougausse, a primitive, but highly lethal form of landmine.