A daring but costly British raid kept the Nazis from repairing their biggest warship

• By spring 1942, the British had blunted the Nazi advance but still faced a desperate situation.
• British leaders feared the German navy, especially the battleship Tirpitz, wreaking havoc on Allied convoys.
• To keep Tirpitz out of the Atlantic, the British mounted high-risk raid on the only facility that could repair it.

Shortly after 1:00 a.m. on March 28, 1942, a destroyer flying the German flag and 18 smaller boats entered the Loire River estuary and headed for the German-occupied port of St. Nazaire on France’s Atlantic coast.

The ships were not aggressive and responded correctly to German signals, but the Germans were suspicious.

Although the destroyer appeared to be of German design, the smaller boats looked different, and they all sailed in the middle of the estuary, the shallowest part, rather than in the deeper channel closer to the coast that vessels normally used.

The ships were in fact British. They carried teams of elite commandos with a critical mission: destroy St. Nazaire’s massive dry dock to prevent the Germans from using it to repair the battleship Tirpitz.

As the British ships approached, their cover was blown, and German guns on both sides of the estuary opened fire. Shedding their disguise, the British sailed the destroyer at full speed toward the dry dock.

The target

By spring 1942, the British had survived the Battle of Britain and opened a second front in North Africa but still faced a desperate situation.

The Battle of the Atlantic was raging, and German U-boats were wreaking havoc on Allied convoys. After Japan declared war on them in December 1941, Britain and the US had to divert warships to the Pacific.

The Royal Navy had sunk the Kriegsmarine’s crown jewel, the battleship Bismarck, in May 1941, but its sister ship, Tirpitz, was now active.

Tirpitz’s deployment to Norway in January 1942 had unnerved the British, who worried it might attempt to enter the Atlantic, as Bismarck tried to do.

To prevent that, the British decided to destroy the only place where Tirpitz could have major repairs done: the dry dock at St. Nazaire. Built in the 1930s for the massive French ocean liner SS Normandie, it was nearly 1,000 feet long, 164 feet wide, and more than 50 feet deep.

St. Nazaire had become an important base for the Kriegsmarine’s U-boat fleet, and reaching the dry dock, which was about 6 miles from the mouth of the estuary, would not be easy.

In addition to about 80 anti-aircraft guns and a 5,000-troop garrison, the dry dock was defended by anti-submarine and torpedo nets, coastal artillery, mines, and patrol vessels.

An air raid or a bombardment by warships were simply too risky and weren’t guaranteed to destroy the dry dock. The British instead devised a commando raid using the destroyer HMS Campbeltown and 18 motor launches.

Campbeltown — a US Navy destroyer given to the British in the Destroyers for Bases Agreement of 1940 — had two of its funnels removed and the other two cut at an angle in order to look like a German Möwe-class torpedo boat. It was also loaded with 4 tons of explosives on a time-delay fuse.

Campbeltown would ram the center of the dry dock’s gate. The commandos aboard the destroyer and the motor launches would then disembark and destroy the dry dock’s machinery and other harbor facilities before evacuating on the launches. The explosives on Campbeltown would then detonate, destroying the gate and flooding the dry dock.

It was an extremely risky plan that many high-ranking British military officials thought was impossible.

Vice Adm. Lord Louis Mountbatten — chief of Combined Operations Headquarters, which had been set up to harass the Germans with raids — insisted it would work, arguing the presumed impossibility in fact made it possible.

“The Germans will never think we’ll attempt it,” Mountbatten said.

The raid

In all, 265 commandos and 346 Royal Navy personnel were assembled for the mission. Before they departed England, Mountbatten offered them a chance to opt out of the mission without any consequences. None did.

After being escorted to France by other Royal Navy destroyers, the force made its way into the Loire estuary, where they used a captured German codebook to deceive the port’s defenders.

But 2,000 yards from the dry dock’s gate, Germans on both sides of the estuary opened fire, killing scores of British commandos and sailors and sinking several motor launches.

Despite the heavy fire, Campbeltown broke through the gate at 1:34 a.m., with about 32 feet of the 314-foot warship protruding into the dock.

The surviving commandos swarmed the port and destroyed the dry dock’s pumps and operating mechanisms. They then regrouped to evacuate, but the motor launches had either been destroyed or had already left.

Stranded, the remaining commandos attempted to fight their way out in small groups and escape to neutral Spain. Most were soon captured, though five eventually did make it to Spanish territory.

Several hours later, as German soldiers were inspecting Campbeltown and the damage to the dry dock, the destroyer exploded. The detonation was hours late, but it destroyed the gate, killing scores of Germans and two captured commandos.

The operation came with a steep price. Sixty-four commandos and 105 sailors were killed, while more than 200 other raiders were captured. About 400 Germans were killed.

Despite the losses, the mission was successful. The dry dock was so damaged that it wouldn’t be repaired until after the war, and Tirpitz stayed in Norway until British aircraft sunk it on November 12, 1944.

Months after attacking St. Nazaire, Mountbatten led another raid on France. The August 1942 attempt to attack and briefly hold the port of Dieppe was repulsed with disastrous losses, but it yielded lessons applied directly to the Normandy landings two years later.