Successful amphibious assaults create a misleading sample because attackers normally launch them only after assembling enough power to expect success. Coastal defences can still be valuable by narrowing the attacker's choices, forcing a larger expedition, and delaying progress until naval or land forces respond. States also relied more heavily on fortifications when they lacked mobile naval power, as late-war Japan did after its fleet's operational reach contracted. Germany's losses of experienced destroyer personnel offer a related example of how missing naval capacity could persist.
Chapter · 1:26-5:23
Why coastal defences did not need to stop every invasion
Coastal fortifications can restrict landing options, raise the force threshold, and buy time without making a coast impenetrable.