Operation Principal was one of the most daring special operations undertaken by the Royal Navy during the Second World War. Planned jointly by the Royal Navy's Submarine Service and Combined Operations Headquarters, the mission aimed to attack major Italian warships inside heavily defended Mediterranean harbours using Chariot manned torpedoes. The operation was launched from Malta in December 1942 and demonstrated both the ingenuity and determination of the Allied submarine campaign.
Although only limited tactical success was achieved, Operation Principal became one of the most ambitious underwater assault missions of the war. It also marked the final patrol of HMS P.311, which disappeared with all hands while carrying Chariot crews towards the Italian naval base at La Maddalena.
Operation Principal at a Glance
| Operation | Operation Principal |
|---|---|
| Dates | 28 December 1942 – January 1943 |
| Launch Base | Malta (10th Submarine Flotilla) |
| Objective | Attack Italian warships in the naval bases of La Maddalena and Palermo using Chariot manned torpedoes. |
| Royal Navy Units | HMS P.311 and Combined Operations Chariot teams. |
| Primary Targets | Italian heavy cruisers Gorizia and Trieste, together with other Axis vessels. |
| Result | Limited success at Palermo. HMS P.311 was lost with all hands before reaching La Maddalena. |
| Historical Significance | One of the Royal Navy's most ambitious special submarine operations of the Second World War and one of the earliest large-scale uses of Chariot human torpedoes. |
The Strategic Situation
By the end of 1942, the strategic balance in the Mediterranean had changed dramatically. The successful defence of Malta and the arrival of vital supplies following Operation Pedestal allowed the island once again to become an offensive naval base. From Grand Harbour, submarines of the famous 10th Submarine Flotilla resumed relentless attacks against Axis shipping carrying reinforcements, fuel and ammunition to North Africa.
At the same time, the Royal Navy sought new ways of attacking heavily defended enemy warships that rarely ventured into open waters. Conventional submarine attacks inside naval bases were almost impossible because of anti-submarine nets, minefields, searchlights and constant patrols. Combined Operations therefore developed an entirely different approach using human-guided torpedoes.
The Chariot Human Torpedo
The Chariot was a British development inspired by the Italian Siluro a Lenta Corsa ("slow-running torpedo"), better known as the famous "human torpedo". Two divers rode the electrically powered weapon, steering it underwater towards enemy ships while wearing breathing apparatus. Once beneath the target, they detached a large explosive charge which was fixed to the hull before the operators attempted to escape.
Although extremely dangerous, the Chariot offered the possibility of striking major warships inside protected anchorages where conventional submarines could not penetrate. The weapons required specially modified submarines capable of transporting them externally in watertight cylinders before releasing the crews close to the target.
HMS P.311 and the Mission
For Operation Principal, the Royal Navy selected HMS P.311, a Third Group T-class submarine specially modified to carry Chariot equipment. She became unique among British submarines, being adapted specifically for clandestine assault operations rather than conventional torpedo attacks.
Commanded by Lieutenant Commander Richard Douglas Cayley, DSO and Two Bars, P.311 sailed from Malta on 28 December 1942. Her destination was the Italian naval base at La Maddalena on Sardinia, where intelligence indicated that the heavy cruisers Gorizia and Trieste were lying at anchor.
The plan called for P.311 to approach the harbour under cover of darkness before releasing her Chariot crews several miles from the entrance. The divers would then navigate through harbour defences and attach explosive charges beneath the enemy cruisers before escaping to a rendezvous point.
Simultaneous Attacks
Operation Principal was not limited to La Maddalena. At the same time, other Chariot teams were transported to attack Axis shipping in the harbour of Palermo. These simultaneous operations were intended to stretch Italian defences and increase the chances of success by striking multiple naval targets on the same night.
While the Palermo teams succeeded in entering the harbour and damaging several vessels, events at La Maddalena took a very different course.
The Loss of HMS P.311
After leaving Malta on 28 December 1942, HMS P.311 proceeded towards La Maddalena carrying two Chariot crews and their equipment. The submarine transmitted her final signal on 31 December while approaching the northern coast of Sardinia. No further communications were ever received.
For many years the fate of P.311 remained one of the greatest mysteries of the Mediterranean submarine campaign. It is now accepted that she struck an Italian defensive mine before reaching the launch position for the Chariot attack. The submarine sank with all sixty-one members of her crew, together with the embarked Chariot operators, before the operation could begin.
In May 2016, Italian divers located the wreck lying upright on the seabed approximately twelve miles north-east of Tavolara Island, Sardinia, at a depth of around one hundred metres. The submarine was found largely intact, with her Chariot containers still secured to the casing, confirming that the assault teams had never been launched.
The Palermo Attack
While HMS P.311 was making her approach to La Maddalena, other Chariot teams carried out simultaneous attacks against enemy shipping in Palermo Harbour. Despite extremely hazardous conditions, several operators succeeded in penetrating the harbour defences and placing explosive charges beneath their targets.
The attacks damaged a number of Axis vessels and demonstrated that the Chariot concept was capable of succeeding against strongly defended ports. However, the loss of P.311 and the capture of many of the assault teams highlighted the immense risks involved in these pioneering underwater operations.
Legacy
Although Operation Principal achieved only limited military success, it represented a remarkable combination of submarine warfare, naval intelligence and special operations. The courage displayed by the crews of the submarines and the Chariot operators reflected the determination of the Royal Navy to strike enemy forces wherever they were found.
For Malta, the operation demonstrated the continuing importance of the island following the lifting of the siege in 1942. Once again supplied and operational, the 10th Submarine Flotilla was able to launch offensive patrols and clandestine missions deep into enemy-controlled waters, maintaining constant pressure on Axis naval and merchant shipping throughout the Mediterranean.
The sacrifice of the crew of HMS P.311 is commemorated on the Malta Submarine Memorial at Fort St Elmo, where their names appear alongside those of the many Allied submariners who never returned from patrol. Their story remains one of the most poignant episodes in the history of Malta's wartime submarine service.
Related Pages
Sources
- Malta Defiant & Triumphant – Rolls of Honour 1940–1943.
- Roskill, S.W. The War at Sea 1939–1945.
- Kemp, Paul. Underwater Warriors.
- National Archives (UK) – Admiralty Records.
- Commonwealth War Graves Commission.
- Royal Navy Submarine Museum.
- Uboat.net – Allied Warships.