Once again, this time in Afghanistan, "the Marines have landed and the situation is well in hand." Farther inland than they went to reach Mexico City in 1847, Marines again proved to be agile and capable instruments of national power. However, among the effects of their capability has been erosion of one of the original purposes of the Marine Corps—security of ships and naval bases. The effects of this transformation of its security force into another army are painfully apparent to the Navy.
When the Romans invented the boarding ramp, ships' main armament shifted from the ram to hand-to-hand fighting—those outfitted for and dedicated to this work were marines. With the introduction of cannon, marines became less an offensive arm and more a disciplinary force to maintain order in shipboard populations composed primarily of slaves and criminals. While useful as sharpshooters, they served principally to protect captains from their crews. As society mellowed and sailors became more disciplined, marines transmuted into a "weapon system" that protected the ship in port and served as a force immediately at hand in foreign waters.