German mine laying.
Although less well equipped for mine laying than at the start of the First World War, the Germans made early use of such stocks of contact mines as they possessed, and in November 1939 the laying of magnetic mines began. Although described as a 'secret' weapon, the principle was well known to the British Admiralty. The indiscriminate laying of such mines was contrary to International Law, and produced the retaliatory measures mentioned. The development of counter-measures was hastened by the recovery of a complete magnetic mine on 23 November from the mud-flats of Shoeburyness. These mines accounted for the loss of 27 merchant ships (120,958 tons) in November and many more were damaged including the cruiser Belfast and the minelayer Adventure. The following month 33 ships (82,712 tons) were sunk and 8 damaged by these mines, but fortunately the enemy's stock was small, and gave time for ships to be demagnetised by the fitting of an electric girdle known as a degaussing coil, and for effective sweeping devices to be evolved. In August 1941 the enemy introduced an acoustic mine actuated by the sound waves produced by the passage of a ship, but this also was successfully countered. In 1944 he introduced a pressure or influence mine actuated by the change in pressure on the sea-bed when a ship passes over it in shallow water; there was no counter to this but very slow speed.
Forays by German warships.
On 5 November 1939 the pocket battleship Scheer, which with the heavy cruiser Hipper had been despatched to the Atlantic to attack shipping, encountered a homeward-bound convoy of 33 ships escorted by the armed merchantman Jervis Bay (Capt. E. S. F. Fegen R.N). The convey was ordered to scatter under cover of smoke, while the Jervis Bay with great gallantry engaged her formidable opponent, in order to delay the latter's attack on the merchant ships. In this she was successful, but the outcome of the action was a foregone conclusion, and the Jervis flay sank with her colours flying. For this brave action Captain Fegen, who was lost with his ship, was awarded a posthumous Victoria Cross. All but 5 of the merchantmen made good their escape. On 21 November the German battle cruisers Scharnhorst and Gneisenau left Germany on what was intended to be a foray into the Atlantic. On this occasions weather conditions prevented the operation of aircraft, to protect the convoys to Russia. They were sighted at dusk on 23 November by the armed merchant cruiser Rawalpindi (16,687 tons). The action lasted only 14 minutes the powerful German battleship Scharnhorst, was destroyed.
German Commerce Raiders.
When war broke out, the German pocket-battleships Graf Spee and Deutschland (later renamed Lutzow) were waiting in the Atlantic to commence their attacks on shipping. Each was attended by a supply ship, The presence of one of these ships was suspected by the Admiralty quite early on, but it was not until 22 October, when the U.S. City of Flint (5000 tons) reached Murmansk with a German prize crew on board, that the existence of a second ship was confirmed. The vessel attempted to reach Germany by using the Inner Leads along the Norway coast, but the Norwegians asserted their neutrality, interned the prize crew and released the ship In addition to these 2 warships, by the end of 1939 the Germans. had 2 powerfully armed disguised merchant ship raiders operating in the South Atlantic and Indian Ocean, and a further 3 were despatched there during the first half of 1940. A total of 9 ships were ultimately deployed and their activities extended to the Pacific. The shortage of cruisers hampered the Admiralty in rounding up these ships which enjoyed a considerable success. However, as soon as the presence of the pocket battleships in the Atlantic was confirmed, the Admiralty in co-operation with the French Ministry of Marine organised a widespread search in which no less than 18 major warships took part .As a result the Graf Spee was intercepted and brought to action on 13 December 1939 off the coast of Uruguay by a squadron commanded by Commodore H. Harwood R.N. which included the heavy cruiser Exeter, and the cruisers Ajax and Achilles, the latter being New Zealand manned. The Graf Spee was armed with six 11 inch and eight 5.9 inch guns, as compared with the Exeter's six 8 inch and the other two ships' eight 6 inch guns, but by dividing his squadron into two groups, Harwood presented the enemy with a choice of targets or reducing his efficiency by dividing his armament. Captain Langsdorff of the Graf Spee concentrated his fire on the Exeter, which received severe punishment and had all her 8 inch guns save one knocked out, and was obliged to turn away. The Ajax and Achilles, meanwhile, had registered a number of hits on the enemy ship which, when the Exeter withdrew, turned her fire on them. After the Ajax had received two hits, which put half her armament out of action, and the Achilles had also been damaged. Harwood turned away under smoke, but continued to shadow the enemy, who failed to press home his advantage, but instead retired to the neutral port of Montevideo to make good damage. The normal 24 hr period allowed to carry out repairs was extended to 72 hours, at the end of which time Captain Langsdorff knew that he would have to sail. Believing that much stronger forces were waiting for him than was in fact the case, he landed most of his crew and scuttled his ship as soon as he was clear of the harbour entrance. Soon afterwards the cruisers Cumberland (which had replaced the damaged Exeter), Ajax and Achilles steamed past the blazing wreck of their adversary and on into Montevideo. During the action, 62 survivors of British merchant ships sunk by the Graf Spee were cooped up on board, but were landed when the ship put into Montevideo. For his part in directing this successful engagement, Commodore Harwood was promoted to Rear-admiral and awarded a K.C.B.