CLEARING THE COASTS

As an island nation, Britain's access to maritime trade routes was vital to its survival and they became a prime target for German mining efforts

During the Second World War, particularly the early years, there were several threats to Britain’s vital mercantile traffic: enemy aircraft, ships and submarines. And in the coastal waters surrounding the country lurked another danger – mines.

During the First World War, Germany had deployed 25,000 mines in British waters, sinking 259 merchant vessels. To counter this threat the Royal Navy (RN) eventually amassed a force of 726 minesweepers in home waters. Yet on 3 September 1939, despite the last-minute requisitioning of trawlers for conversion to minesweeping duties and the re-emergence of First World War-era minesweepers from Reserve, the RN’s active minesweeping force comprised just 29 Fleet minesweepers and 25 minesweeping trawlers.

The first losses to mines in British coastal waters occurred on 10 September when the SS Magdepur and SS Goodwood were sunk in the vital East Coast War Channel. Other losses soon followed, but all these early sinkings were in waters that had been swept and re-swept. As losses and concerns soared, it was clear something was going wrong. The answer lay in Germany’s advanced development of the magnetic mine during the inter-war years.

The magnetic mine was not a German invention; it had first been developed – and deployed – by Britain in 1918. However Germany had taken the technology forward in the 1930s whereas RN interest had lapsed, so while RN sweepers were well-practised in sweeping for ‘conventional’ moored, contact mines with which they were already familiar, they had no effective means of countering magnetic mines, which were taking a heavy toll on shipping around the coast.