The Naval Commands most likely to face the invasion were Nore, Dover and Portsmouth. The Operational Plan for Nore Command to counter the invasion threat is particularly detailed.
Left: Naval and Coastal Command Areas
Nore Command (Operational Order “P.E” or in short “Purge” – Aug 26th 1940)
Striking forces available to Nore Command included destroyer flotillas at Humber, Harwich and Sheerness. Motor torpedo boats were based at Felixstowe. Intermittent destroyer night patrols were operated off the Humber, off the Suffolk coast and off Margate. Minesweeping flotillas would keep the searched channels clear and at night patrol to prevent mine laying. Auxiliary patrols operated about five miles from land, from Flamborough Head to the River Crouch and from Whitstable to North Foreland. Vital to Nore Command’s success would be fighter support – the primary role of Fighter Command would have to be to destroy bombers and dive-bombers attempting to attack the vessels of Nore Command.
The first role of the Navy was to destroy the enemy tanks and troops before they could get ashore. As tanks posed the greatest threat, tank transports were to be the first priority. Enemy escorts were to be ignored unless they needed to be engaged first to get at the transports. The general instruction was “no Captain can do very wrong if he engages enemy transports at close range” – an obvious play on Nelson’s Trafalgar memorandum of Oct 9th 1805 when he wrote “….no Captain can do very wrong if he places his ship alongside that of an enemy”.
If an indication of a landing was received the warning “Stand by “Purge” (location)” would be issued. If a landing was in progress the signal “Carry out Operation “Purge”” would be issued. On receipt of the signal all vessels in the threatened area would proceed immediately to the attack.
Locations in respect of this signal were: Area I – North of Flamborough Head; Area II – Flamborough Head to Skegness; Area III – Skegness to Brancaster; Area IV – Brancaster to Lowestoft; Area V – Lowestoft to Brightlingsea; Area VI- Foulness to Shoebury; Area VII – Nore; Area VIII – Sheppy to Thanet; Area IX – Dover.
Cruisers, destroyers and motor torpedo boats would at first be under command of C.I.C Nore Command but it was expected that when the enemy was engaged it would be down to the initiative of local commanders. Auxiliary patrol vessels would be under the command of Flag and senior officers in command of the area. Additional support would be provided by convoy escorts if the convoy was within 30 to 40 miles of the position in which the enemy was reported. Any units at sea and not in contact with the enemy, and if no specific orders were received, were expected to ‘March to the sound of the Guns’ i.e. head to the nearest area in which the enemy were known to be attempting a landing.
If ships ran short of fuel or ammunition they were to return to the most convenient port to replenish and then set to sea again to engage the enemy. This would be critical if the enemy invasion fleet numbered hundreds of steamers and perhaps thousands of barges – a quick turn around would be vital. If enemy ships entered an estuary or harbour, ships were to follow and destroy them. If a destroyer or larger ship was mined or torpedoed it was up to the smaller vessels to pick up survivors – on no account were destroyers to stop to help if this would delay its attack on the enemy.
It was expected that ports in Nore Command should carry out regular exercises to test “Operation Purge” – a rapid sweep of the exit channel then get all vessels out to sea as soon as possible.
Instructions for destroyers: