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You want rifle infantry in thin lines to maximize firepower. Columns of anything can be wrecked by the modern artillery. The old style melee troops can be useful provided they are not subjected to much gunfire prior to contact. Such gunfire will be hard to avoid if the enemy has the kneel tech.

Kneel firing infantry is very powerful.

Troops can skirmish and indeed, the sharpshooters outrange other infantry. Only terrain can protect a target from artillery, though. Set up a skirmish and see what the guns do to approaching formations. Parrotts and Armstrongs are deadly. Gatlings are less so only for having a shorter range.