HMS Campbeltown

In May 28th 1942, the British conducted a commando raid against Nazi-occupied France. The British wanted to strike at this target as it was the only major German controlled dock on the Atlantic. British commandos landed in the dock and proceeded to wreak havoc. Eventually, having caused considerable damage, yet having not totally destroyed the dock, the commandos retreated having lost 169 men.

The HSM Campbeltown, run aground
in the docks, minutes before it exploded

They left behind the HMS Campbeltown, an obsolete battleship that was originally American but was transferred to the British in 1940. It sat in the dock, seemingly abandoned until around noon, when the ship exploded, destroying the dock and killing 239 Germans soldiers and 251 French civilians.

The ship had been intentionally packed with explosives and left as a sort of time-bomb in the docks. All in all, the raid was a great success.