In 1947, the British navy set off one of the largest non-nuclear explosions in history in an attempt to destroy German military fortifications on Heligoland.
Heligoland has long been an island of strategic importance. It sits in the North Sea off the shores of Germany and Denmark, close to the point where the River Elbe meets the ocean. Control of the island bounced between the Scandinavians and the Germans until 1807, when the British annexed it during the Napoleonic Wars. Heligoland, it turned out, was a great place to smuggle secret agents into the continent; head up the Elbe and you can access Hamburg, Magdeburg, and Dresden with ease.
In the 19th century the island became a popular holiday destination; the German national anthem was composed here; Werner Heisenburg supposedly came up with the idea for quantum mechanics while on vacation here too. Control of Heligoland returned to Germany in 1890, as part of a treaty that recognised British authority over Zanzibar. (I wrote about the Heligoland-Zanzibar Treaty – and how it led to the shortest war in history – back in 2020.) The island was evacuated during World War II and then came under British control at the end of the war.
So, by 1947 the British navy controlled a very small German island in the North Sea. It was no longer as strategically important as it had been in the pre-aeroplane era, but it still housed several German fortifications. So the British decided to blow it up.
Now, I’ve seen some accounts that the British thought they could destroy the whole island – whereas others say they were only trying to destroy the military buildings, or just dispose of leftover WWII ammunition. Either way, they packed the island with explosives. A lot of explosives. Tonnes of explosives.
The result was one of the largest non-nuclear explosions in history. It did not destroy the island, but it did leave a huge crater that’s still visible today:
The island returned to German control in 1952, and today it’s a popular tourist destination once again.