John K. Mahon and Romana Danysh, CMH 60-3: Infantry, Part I: Regular Army…
“ They were simply composed of men picked for their strength and courage. The truth is that conditions in America did not favor the specialization of particular companies. Indian wars had to be fought by whatever troops were available; there was no time to await the arrival of elite corps, whether called grenadiers or something else. Nor did fights with Indians give much opportunity for infantry to assume the formal line of battle with light units out front. Finally, the scattering of the companies of Regular regiments made specialized training impossible. ”
