Maritime mobility made Wellington’s campaign viable

Moving a siege train by sea avoided bottlenecks, ambushes, and the poor roads that constrained land columns in Spain and Portugal. The naval system also contributed intelligence, freedom of manoeuvre, sailors, and guns when the army lacked its own heavy artillery. Sea power supported the Lines of Torres Vedras and secured a flank that an entirely land-based system could not sustain as effectively. Sir Home Popham's coastal raids further forced the French to protect their rear areas instead of concentrating every available unit against Wellington.