Naval - Operation Plans

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:

  • Any destroyer on patrol at night was to proceed and immediately attack the enemy. During daylight it would rendezvous with the nearest approaching destroyers.
  • The Humber fleet was to set to sea. If enemy forces were steering between Flamborough Head and Cromer it would proceed to attack the enemy. If not it would proceed to the Outer Dowsing Light Float to await further instructions.
  • The Harwich fleet was to set to sea. If enemy forces were reported between Great Yarmouth and Brightlingsea it would proceed to attack the enemy. If not it would proceed to the Aldeburgh Light Float and await further instructions.
  • The Sheerness fleet would set to sea and concentrate off Southend if no other orders received.
  • The Margate force would set to sea and proceed to attack the enemy if he was reported between The Swale and North Foreland.
    • Instructions for motor torpedo boats (MTB’s)

      • If sufficient warning was obtained, MTB’s were to proceed to attack the enemy in the East Coast Mine Barrier where there was sufficient depth of water to use torpedoes. Otherwise they were to proceed to their lookout positions and await further instructions.
      • The primary role of MTB’s was to use their torpedoes on the largest transports they could get to. Torpedoes were to be fired at close range to ensure hits. When torpedoes were exhausted, they were to use their machine guns to engage smaller transports and E boats.
      • If present, M.A/S.B’s (Motor Anti-submarine Boat – usually known as “Masby") were to attack transports and E boats with their machine guns although the possibility of dropping depth charges close in front of larger vessels should also be borne in mind.
        •   Top left: "D" Class MTB. Bottom left: Seventy-foot MTB
            Right: German Schnellboot (fast boat) - known as the
            E boat (abbreviation of "Enemy War Motorboat")

          Some tactical notes on Operation “P.E” were also issued. If sufficient warning was obtained the best place to engage the enemy invasion flotillas was immediately west of the Mine Barrier – if the German fleet retired it would have to pass back through the Barrier. It was recommended that destroyers operate in divisions of three or four. Any detached destroyers would have to weigh up the pros and cons of each situation before deciding to concentrate prior to attacking. It was noted that in conditions of bad visibility, destroyers and other vessels could ram any larger warship (from amidships aft to the propellers). Capture by boarding was also an option although both these forms of attack should only be considered after all the transports had been dealt with.

          A memo dated Sept 19th detailed some of the realities of the situation facing Nore Command. It was recognized that the minesweeping flotillas and other smaller vessels were weak forces. Only six or seven motor torpedo boats could be expected to be available. The number of torpedoes carried on destroyers and cruisers was “regrettably low”. The C.I.C Nore Command recognized that his duty would also include repelling an invasion outside the Nore Command, particularly from Ramsgate to Portsmouth. Any fleet moving from Nore Command through the Dover Straights into the Channel was expected to suffer heavily from dive bombing attacks.

          Portsmouth Command

          In May 1940 when a large raid by troops landing in fast motor boats, which could be beached, was considered a possibility, Portsmouth Command issued instructions ‘Operation J.B’ to deal with this threat. Offshore patrols were to be established to give warning of any enemy movements. All armed vessels were placed at short notice to go to any threatened area.

          Patrols were established in the areas:

          Patrol A – Dungeness to Beachy Head; Patrol B – Beachy Head to Owers; Patrol C – St Catherine’s point to Durlstone Point; Patrol D – Durlstone point to Portland; patrol E – Portland to Lyme Regis.

          The main aim of the patrols was accurate reporting. On the first indication of a landing C.I.C Portsmouth would issue the order to all vessels:”Stand By for Operation J.B”. On receipt of this all smaller vessels were to raise steam for full speed and larger vessels were to proceed to anchor at Spithead. If an actual invasion / raid occurred the signal “Operation J.B – (locality)” would be issued to all vessels which would be expected to mount rapid attacks, using commanders own initiative, on the threatened area.

          In June to counter the threat of the enemy moving vessels down to his new bases in Western France and to counter the threat by E Boats, Portsmouth Command issued instructions for ‘Operation J.C’. The object was to intercept and destroy any enemy forces encountered by destroyer patrols. Destroyers were to leave the seaward end of the searched channel after sunset and proceed to within 10 miles of the French coast, carry out a sweep of the coast and leave the vicinity of the French coast before daylight, returning to Portsmouth.

          The patrol routes were as follows:

          • Patrol J.C West: leave end of Western Searched Channel at 2200 hrs. To be in position 8’-10’ north of Cherbourg at 2400 hrs. Sweep to Le Harve. Set course for Portsmouth at 0300 hrs. Enter searched channel at 0700 hrs
          • Patrol J.C East: Leave end of Eastern Searched Channel at 2200 hrs. To be in position 10-15 miles NW of Cape de La Heve at 2400 hrs. Sweep towards Dieppe. Set course to Portsmouth at 0300 hrs. Enter searched channel at 0700 hrs.
            • It was anticipated that the enemy would mine the Channel to prevent the movement of the Royal Navy. The operation to keep the searched channel clear of mines was named ‘Operation J.E’.

              Dover Command

              Dover Command also operated patrols in June, known as ’OD Patrols’, with the aim of preventing minelayers and submarines operating in the convoy routes. During July destroyers were sent out on ‘OE Patrols’, leaving harbour at dusk to ‘deal with any invading forces entering the Straits of Dover’, especially E Boats. Towards the end of July, a number of destroyers were sunk or damaged and as a result the flotilla was moved to Portsmouth. Patrols from Portsmouth covered the Dover Straights until October when Nore Command was then instructed to operate ‘an intermittent patrol of two or three destroyers on two nights a week and whenever weather conditions and intelligence suggested the enemy might be encountered’.


              We shall fight on the Beaches, B Lavery, Conway, 2009
              Admiralty papers on Invasion, TNA

e boat
torpedoe boat1
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