These muskets-armed troops are use massed volleys to break an enemy, relying on discipline to withstand any counter fire.
“Marching regiments” or “line battalions” make up the majority of units in European-style armies. They are so called because they form the line of battle, not because they always deploy in lines. Indeed, over time the capabilities of line infantry should improve as new tactics, drill and weaponry are developed. These soldiers carry muzzle-loading, smoothbore muskets firing lead balls as wide as a man’s thumb. These are inaccurate weapons, effective only over 200 paces or so and when fired in massed volleys. The ability to fire and reload with machine-like regularity with shot and bullet flying and comrades falling all around is what wins battles.
Historically, in many armies colonels received a fee to raise regiments, which remained their personal property and commands. They jealously guarded their rights to appoint friends, relatives and hangers-on as regimental officers. This contractor system, however, allowed unscrupulous officers to make handsome profits by pocketing the pay of non-existent soldiers. The better colonels did take a pride in their regiments, spending their own fortunes on good uniforms and weapons. The capabilities of a “standard” line infantry unit therefore varied between nations and over time. It wasn’t until the 1760's that anything approaching uniformity of drill, equipment and regulations became the norm.
Colonial line infantry are almost the exact same as regular line infantry, except that the regular line infantry can cope with morale shocks easier than colonial line infantry can, and usually have better stats depending on faction. Unlike regular line infantry, colonial line infantry is the same for every faction - meaning they can have tactical uses for some nations such as Russia, who have line infantry who are strong in melee but weak at range. They are also the only colonial unit that suffers from heat fatigue.