Sea supply frustrates a siege

How did Royal Navy supply affect French attempts to besiege defended ports?

Naval delivery kept ports supplied in large quantities, preventing the French from fully isolating them and undermining the siege.

Gibraltar and Lisbon connect naval logistics directly to land warfare. A siege depends on cutting the defender off, but secure maritime access can keep a port supplied at a scale difficult to match over roads. Ships can deliver greater quantities with less dependence on vulnerable overland routes. Sea control therefore changes whether an apparently encircled position is truly isolated and can make a land siege strategically incomplete.