Action of 4 April 1941

The Action of 4 April 1941 was a naval battle fought during the Atlantic Campaign of the Second World War. A German commerce raider encountered a British auxiliary cruiser and sank her with heavy losses after an hour of fighting.

Background
The Kriegsmarine auxiliary cruiser GERMAN AUXILIARY CRUISER Thor was raiding in the mid Atlantic in early 1941. On that cruise, the Germans engaged two other British armed merchant cruisers (HMS Alcantara and HMS Carnavon Castle) in surface battles but they ended indecisively. So when Thor encountered HMS Voltaire, her crew were already battle tested and anxious to sink an enemy combatant. Thor was 122 m long and weighed 9200 LT, she was armed with six 150 mm, two 37 mm and four 20 mm naval guns along with four 533 mm torpedo tubes. The raider also carried an Arado Ar 196A-1 floatplane for reconnaissance and had a complement of 349 officers and crewmen.

HMS Voltaire was larger than the raider—displacing 13245 LT—but with a smaller crew of 269 men and officers. She had eight 152 mm and two 76 mm naval guns, including at least one anti-aircraft mount. Thor was returning to Germany when she found Voltaire heading to Freetown about 900 mi southwest of the Cape Verde Islands.

Action
It was about 06:15 on 4 April when crewmen of Thor spotted smoke on the horizon. Captain Otto Kähler assumed the vessel to be a coal burning ship so he altered course into the direction of the smoke. When the Germans were able to make visual contact with HMS Voltaire, they suspected she was a neutral ocean liner as she did not attempt to escape. The British—under Captain J.A. Blackburn—sighted the approaching Germans coming head on, so they fired a burst of anti-aircraft fire as signal for identification. A signal from Thor was not returned, but the British soon discovered the identity of the approaching ship at about 06:45, when it replaced the flag of Greece with a German naval ensign and fired a shot across Voltaire's bow. The British responded by manning their guns and firing a broadside with their mixed armament, but to no avail; they were outgunned and outranged.

After only four minutes of dueling at around 9000 m away, the Germans began striking Voltaire with their 150 mm guns. The first shots entered the radio room and the generator room of Voltaire, heavily damaging the vessel, knocking out communications and steering gear and putting her into a list. Heavy fires also broke out and nearly covered the entire deck of the British ship. Despite the fire the Royal Navy gunners continued fighting for nearly an hour. For the next several minutes, the two sides fired; only one British shot managed to hit Thor, and it caused no casualties, the shot tearing off some radio equipment attached to the main mast. By 07:15, only two of the British 152 mm guns were in action, while Thor circled around Voltaire, firing rapidly.

At 08:00, the German's 150 mm guns overheated so Captain Kähler decided on a torpedo attack to end the engagement. But just as Thor was lining up to fire a spread, a white flag was observed aboard Voltaire and so the firing ceased. Captain Blackburn—having lost 72 men killed in action—gave the order to abandon ship and for the next five hours the Germans rescued 197 survivors, two of whom died later on and the rest became prisoners of war. Kähler also recorded that half of the rescued sailors were wounded. After the battle, Thor continued on to Germany to refit for a second raiding voyage. She had fired 724 rounds in a 55 minute battle, more than 50 percent of her ammunition.