In March 1941, over 500 British and Allied commandos, sappers, and sailors launched a daring four-pronged raid against Norwegian towns occupied by the German Army. Despite the German forces spotting the commandos 24 hours before the attack, the British suffered only one casualty.
An officer accidentally shot himself in the thigh.
Operation Claymore, as it was known, was a commando raid targeting fish oil factories in the Lofoten Islands. The fish oil was a prime source of glycerin which is a crucial propellant for most types of weapons ammunition in World War II.
The islands are 100 miles into the Arctic Circle and guarded by a force of over 200 German troops. The commandos expected potentially heavy resistance and spent about a week in the Orkney Islands rehearsing their assault plan.
On March 1, they began a three-day journey through rough seas to the targets. Two days later, they were spotted by a German aircraft but pressed forward, risking the possibility of hitting beaches with prepared and dug-in Nazi defenders.
When the British arrived, ice had formed further out than expected and the commandos were forced to get out of the boats early before running across it to hit the towns. All four groups managed to cross the ice and hit their targeted towns without facing any real resistance.
In fact, the local Norwegians watched the British coming at them like it was a small show, and the commandos made it into the buildings before they even began to see German uniforms. With many of the defenders separated or still asleep, the attackers were able to quell resistance with few shots fired.
They captured 225 prisoners while taking every one of their objectives. Despite the attack force having been spotted by the German plane, none of the defenders were ready.
The grateful locals brought out coffee and treats for the attackers, the sappers planted charges against the fish oil tanks, and the Norwegians started recruiting the citizens into the Free Norwegian Forces.
There was an additional lucky break for the commandos. They hit a German-held trawler and killed 14 of the defenders.
The ship commander managed to throw the Enigma machine over the side but the British still captured technical documents and spare parts for the machine, giving code breakers in Bletchley Park near London a leg up.
The mission was a huge success, but as mentioned above, the British did suffer a single casualty when an officer accidentally shot himself in his thigh with a revolver.
The British knew how well the mission had gone, and got a bit cocky about it.
One group sent a telegraph to Hitler with the captured communication gear asking him where his vaunted German soldiers were. Another group hit a nearby seaplane base and took all their weapons, just for additional giggles.
The German commander, who probably should've been grateful that he and his men weren't added to the 225 prisoners the British had captured, later complained to his fuhrer that the commandos had displayed "unwarlike" behavior.
(Pretty sure the dudes captured without a shot fired were the "unwarlike" fellows, but whatever.)
When the commandos finally left, they blew the fish oil tanks, sending huge fireballs into the sky. They also sank some ships vital to the fish oil production including the most advanced fish factory-ship of the time.