On this day in military history…
in the very early days of the second world war, before the world really understood what a modern sea war would look like, two british warships, HMS Gypsy and HMS Belfast, fell victim to a new type of weapon that no admiral had ever actually seen in combat. german u boats, operating under absolute radio silence, slipped into british coastal waters in the north sea and secretly laid magnetic mines. this was the first time in history that germany had laid magnetic mines directly in british home waters in wartime. unlike a contact mine, these devices did not need to hit the hull. they detected a steel ship’s magnetic field as it passed overhead, then detonated automatically. the british navy had never experienced this before, and nobody had countermeasures ready.
HMS Gypsy was the first destroyer to be lost to the new technology. on the night of 21 november 1939 she was steaming in the humber estuary near grimsby. she passed directly over one of the newly laid german magnetic mines and was blown apart under her forward boiler room. she capsized and sank rapidly in shallow water. thirty men were killed almost instantly or trapped inside the forward compartments. her captain was lieutenant commander guy alec rickards.
that same day the cruiser HMS Belfast, sailing out of the firth of forth, passed over another magnetic mine. the blast tore open her bow, buckled decks and smashed machinery. she lost one man killed and more than thirty wounded. her captain at the time was captain george siborne. she did not sink because of her size and compartmentalisation, but she had to be towed hundreds of miles to devonport for repairs and she was out of the war for nearly three years. although she survived, the damage was a huge shock, because the royal navy realised instantly that this was not a random accident. two major ships, same day, same type of invisible weapon.
the officer responsible for launching this new campaign was kommodore karl doenitz, still at that time subordinate to grand admiral erich raeder, but already shaping the u boat arm into a modern offensive instrument. the mines around the east coast convoy routes were laid largely by u 21 under kapitänleutnant fritz frauenheim, one of the youngest and most aggressive early war u boat commanders. this was the start of what the british later called the east coast war of the mines.
a twist of fate then changed everything. on 23 november 1939, only two days after the Gypsy and Belfast strikes, a magnetic mine was discovered intact on the mud at low tide in the thames estuary. british engineers took it apart and understood the triggering principle. almost instantly the admiralty ordered every steel-hulled ship to be fitted with electric degaussing cables to neutralise its magnetic signature. so ironically the loss and damage suffered by HMS Gypsy and HMS Belfast triggered one of the fastest single leaps in naval defensive science in history.
HMS Belfast survived the war, went on to fight again and served long afterwards. today she still exists, fully preserved as a floating museum ship permanently moored on the river thames in london. and she is free to visit.
