Why amphibious forces need armour and heavy firepower

Amphibious forces can carry siege guns, vehicles, engineers, air defence, and sustained supplies that airborne forces cannot bring in comparable weight. Suitable beaches and harbours are limited, so defenders can prepare the ground and deny an attacker room to manoeuvre. This constraint makes protection and firepower essential for punching through a defended shoreline before lighter troops can exploit the opening. The fleet supplies both heavy equipment and supporting gunfire, allowing a seaborne force to arrive with the combined-arms depth needed to sustain a brigade- or division-scale operation.