How the Royal Navy made a mass invasion findable

Churchill begins by reminding his audience that Britain still has a navy and compares the invasion problem with his Admiralty experience before the First World War. He concedes that the fleet cannot guarantee interception of every small raid, but a force capable of defeating Britain ashore would require a vast transport armada. Five lightly equipped divisions might need roughly 200 to 250 ships, creating a target that air reconnaissance and naval forces could locate and attack. Minefields would narrow the approach routes and force the enemy to expose minesweepers and escorts. Sea power worked through scale, surveillance, interception, and control of access, without promising that nothing could cross the coast.