The maritime aspect of the Battle of Britain: 80 years on
Battle of Britain Day, 15 September, is so designated since it marks the anniversary of the day the tide turned in favour of the RAF in the aerial battle for Britain 80 years ago in 1940.

That day, though a turning point, was by no means the end of the Battle of Britain, which continued until 31 October 1940. The end of the Battle overlapped with the beginning of the Blitzkrieg (‘Lightning War’), shortened in Britain to ‘The Blitz’ – the aerial raids on British towns, cities and infrastructure – which continued on until May 1941, and which included the destruction of Coventry and its Cathedral in November 1940.
The Battle of Britain was not wholly unique in the six long years of the maritime war. Throughout the duration, ships and aircraft attacked one another, but the Battle of Britain saw a significant shift in the conduct and outcomes of the war at sea that was not replicated at any other time within English waters.
The data from Historic England’s National Record of the Historic Environment (NRHE) captures the significance of Battle of Britain over the sea as the RAF sought to intercept and repel the Luftwaffe.
The Battle was fought primarily in the skies over the south-eastern counties of England. Figures for those aircraft recorded as part of the historic environment show that one-third of the aircraft lost on both sides during the Battle of Britain were actually forced down into the sea in English waters, a total of 353 aircraft, of which 217 were German and 136 British.
In turn these 353 aircraft account for 24% – almost one quarter – of all aircraft lost in the sea in English waters during the entire war in Europe from September 1939 to May 1945, a total of 1476 altogether.
The figures for August 1940, perhaps the most acute phase, show that 174 aircraft found a watery grave that month, whether off the south-east coast or in the Thames. For what has become known as ‘The Hardest Day‘, 18 August 1940, when operational losses and destruction of aircraft on the ground, reached their zenith, 12 aircraft are recorded as having been lost in the sea. On the British side the losses that day were four Hurricanes and a Spitfire, while the Luftwaffe lost a He111, four Ju87s, and a Me110.

Eighty years ago today on that first ‘Battle of Britain Day’ on 15 September, the losses had diminished somewhat, all German, and all in the Thames Estuary. That day three Do17s came down: Do17Z (3405) U5+FT crashed and Do17Z (2578) F1+BS was shot down, both off Herne Bay, Kent; Do17Z (1176) 5K+DN was shot down into the Thames.
What is perhaps most distinctive about this phase of the sea war was that during the Battle of Britain aircraft losses within English waters outstripped ships sunk in the same area by roughly 2.5 to 1.
Those figures reveal a completely opposite pattern to the figures available for maritime losses in the other months of 1940: in the previous six months aircraft comprised one-third of maritime losses, and likewise for the remainder of 1940. In other words, there was a unique spike in aircraft lost to the sea.
The Battle of Britain was an aerial battle, stretched out over many long, exhausting, days, weeks and months, but what these figures also show is that during the Battle of Britain the sea war became an air war.