The raid on Pula was an Italian Navy operation conducted during the night of 31 October – 1 November 1918, at the end of World War I. It was carried out by frogmen Lieutenant Colonel Raffaele Rossetti and , who used the Mignatta human torpedo to sink the former flagship of the Austro-Hungarian Navy, the . She was anchored, with several other vessels, in the Adriatic port of Pula–the main naval base of Austria-Hungary. The raid succeeded in sinking the flagship and the abandoned passenger ship Wien, which had been used as a floating barracks until a few days before the raid. An estimated 300–400 crew members were killed when Viribus Unitis sank.
The raid took place during the dissolution of Austria-Hungary and the collapse of its armed forces at the Italian Front, which led the Austro-Hungarian command to request and negotiate the Armistice of Villa Giusti days later. In those circumstances, the Italian government ordered its armed forces to continue to advance as far as possible to occupy the territory that the Allies of World War I promised to Italy under the 1915 Treaty of London in order to entice Italy to join the war. Much of the territory was claimed by the National Council of Slovenes, Croats and Serbs established in Zagreb and claiming to represent the South Slavs living in Austria-Hungary. The National Council sought to unite predominantly South Slavic former Habsburg territories with the independent Kingdom of Serbia in a common South Slavic state by uniting and the independent.
The fleet anchored at Pula, as well as other Austro-Hungarian bases, was handed over to representatives of the National Council the day before the raid. Captain Janko Vuković, an Austro-Hungarian Navy officer, was appointed the commanding officer of the newly acquired fleet and promoted to rear admiral. The National Council declared neutrality in the war and informed the Allies of the new development. And many non-South Slavic crew members left the ships believing the war to be effectively over. Discipline among those who remained aboard was relaxed to the point that the ship was illuminated, and a self-governing sailors' council was established that declared a separate commanding officer for the Viribus Unitis, limiting Vuković's authority.
Rossetti and Paolucci were discovered after placing two explosive devices and captured before the explosion that sank Viribus Unitis. They were briefly interrogated aboard the flagship, released, and then recaptured. They were released on 3 November, when Italian forces arrived in Pula, and later awarded the Gold Medal of Military Valor for the successful execution of the raid.
Background
Over the course of World War I, prewar ideas regarding the political consolidation of South Slav-inhabited parts of Austria-Hungary developed further under the influence of wartime events. Initially, these ideas involved proposals to revise the Compromise of 1867 and introduce trialism in Austria-Hungary — reorganising the country from an empire divided into Austrian- and Hungarian-governed halves into one also comprising a South Slavic-administered area. Those efforts culminated in the unsuccessful 1917 May Declaration championed by Anton Korošec, the leading Slovene (and South Slavic) member of the Imperial Council.
In 1915, the Triple Entente sought to entice the Kingdom of Italy to join the war as an Allied power by offering it various territories, including parts of the Austro-Hungarian eastern Adriatic Sea coast, such as northern Dalmatia and Julian March (including Trieste and Istria), under the Treaty of London. Simultaneously, the Entente offered Serbia Bačka, Bosnia, Herzegovina, parts of Dalmatia, Syrmia, and Slavonia as compensation for territories expected to be offered to Bulgaria to secure its alliance.
A group of politicians, led by Frano Supilo and Ante Trumbić, established the Yugoslav Committee to promote the self-determination of South Slav-inhabited lands from Austria-Hungary. After Serbia failed to persuade the Entente to apply the principle of self-determination to the South Slav lands, the Yugoslav Committee endorsed a political union of the South Slav territories of Austria-Hungary with Serbia and the creation of Yugoslavia, seeing unification as necessary to prevent the partitioning of Croatia between Italy, Serbia, and Hungary. In 1917, representatives of the Yugoslav Committee and the Serbian government issued the Corfu Declaration stating their intent to achieve the union.
In the final days of the war, as the dissolution of Austria-Hungary was unfolding, the National Council of Slovenes, Croats and Serbs, chaired by Korošec, was established as the governing body of South Slavs living in Austria-Hungary. On 29 October 1918, the National Council declared the independence of the State of Slovenes, Croats and Serbs, claiming to represent South Slavs living in Croatia-Slavonia and the city of Rijeka, Dalmatia, Bosnia and Herzegovina, Austrian Littoral (Istria, Trieste, and Gorizia), Carniola, Styria, Carinthia, Bačka, Banat, Baranya, and Međimurje. In a note sent to the governments of the United States, United Kingdom, France, Italy, and Serbia, the Council announced the independence of the newly established state and declared that it was not at war with the Allies.
Prelude Handover of the fleet
On 30 October, Emperor Charles I of Austria ordered the surrender of the Austro-Hungarian Navy, consisting of around 300 vessels, to the National Council. On 31 October, council representatives arrived at the Austro-Hungarian naval bases in Šibenik and Kotor in Dalmatia, and at Pula () in Istria, the main naval facility of the monarchy. Formally, the transfer of the fleet took place in Pula, where Admiral Miklós Horthy met with the National Council delegation led by Ante Tresić Pavičić aboard the flagship and handed the fleet over to them at 9:00 a.m.; at 4:45 p.m., as Horthy left the ship, the Austro-Hungarian flag was replaced by the Croatian tricolour. The navy was formally placed under Admiral Dragutin Prica, whose post remained in Zagreb. Command of the naval base in Pula was assumed by Fregattenkapitän , and command of the fleet was passed to Ship-of-the-Line Captain Janko Vuković; Koch and Vuković were promoted to rear admiral for the occasion. The National Council also sent a message to notify the Allies of the takeover.
Shortly before the handover, the Imperial German Navy forces stationed in Pula withdrew. They vacated the steamship Wien, which they had used as floating barracks, and scuttled three submarines while a fourth sailed to Kiel; their departure was prompted by Austria-Hungary's request for armistice terms from the Allies.
News of the handover
It is uncertain at what point the Italian Navy learned of the transfer of the Austro-Hungarian fleet. According to Achille Rastelli, it became aware of the transfer only after the raid because of delays in transmitting the National Council's message to the Allies; in any case, the message was likely to be dismissed as a hoax, or the transfer would likely be dismissed as unlawful. Fragmentary reports of unusual events in the Austro-Hungarian navy reached Italy on 31 October, but only after 2 p.m. According to Rastelli, Italy learned of the transfer by 1 November, but chose to ignore the information.
A contemporary German report indicates that envoys discussing the armistice terms did not mention the transfer until 4 November. According to the Austro-Hungarian navy representative at the negotiations, Fregattenkapitän Prince Johannes of Liechtenstein, the Supreme Command in Vienna, feared that the negotiations would be jeopardised because the draft terms demanded the surrender of a navy that had already been handed over to the State of Slovenes, Croats and Serbs. Regardless of instructions to the negotiators, the transfer was telegraphed on 1 November by the Chief of Staff of the 10th Army, General , and reported in the Italian press the next day. Even before the fleet transfer, the British had intercepted a message from Vienna to the Austro-Hungarian naval attaché in the Ottoman Empire informing the diplomat of the scheduled transfer, but it was disregarded on the assumption that Italy had a historic right to capture the Austro-Hungarian navy.
Forces involved Although Vuković assumed command of the fleet in Pula, his authority aboard Viribus Unitis was limited. Sailors had mutinied on 28 October and formed councils to govern the port and major ships. The council aboard Viribus Unitis declared the ship's physician, , as the new captain. Convinced the war was effectively over, many non–South Slav crew members left the ship. As crew discipline deteriorated, watertight compartment doors were left open, and several ships in the port—including all three Tegetthoff-class battleships Viribus Unitis, Tegetthoff, and Prinz Eugen—remained fully illuminated.
The Italian raiding force set out from Venice. The attacking component consisted of Regia Marina frogmen Lieutenant Colonel Raffaele Rossetti and , equipped with the Mignatta human torpedo designed by Rossetti. The vehicle used in the raid, numbered S.2, was a converted Schneider A/115 torpedo carrying two limpet mines equipped with time fuzes. Torpedo boats 64 PN and 65 PN provided support, while armed motorboats MAS 94 and MAS 95 towed the human torpedo. The entire force was commanded by Captain Costanzo Ciano aboard one of the support craft.
Timeline Entry into the harbour
The raiding force left at 2 p.m. on 31 October. The human torpedo was carried on the deck of 65 PN to the area near the Brijuni Islands and then towed to the port by MAS 95. At 10 p.m., Rossetti and Paolucci detached the towing cable and proceeded towards the port, reaching its protective barrier half an hour later. By 3 a.m. on 1 November, they had successfully passed through security barriers. The crew of Viribus Unitis likely heard the frogmen moving through water and talking to each other as they entered the port, and briefly used a searchlight to investigate, but a sailors' council representative objected to the unauthorised use of the searchlight and the search was abandoned. Noticing that they may not have sufficient power or time to exit the port before sunrise, Rossetti and Paolucci decided to attack Viribus Unitis and then go ashore. The ship was designated as the primary target, and they knew that it was at the end of a row of anchored vessels. Rosetti and Paolucci planned to wear the Italian officer uniforms that they had on under their wetsuits and proceed on foot to Funtana near Rovinj, where a motorboat was scheduled to pick them up on the nights of 2–7 November.
According to Rossetti, he reached the starboard side of Viribus Unitis at approximately 5 a.m., attached a mine to her hull between the fourth and fifth guns—near what he believed to be close to the engine room—and set the mine timer for 6:30 a.m. As they started to move away, they were spotted, and a motorboat was dispatched to pick them up; while the boat approached, Paolucci activated the second mine. Left attached to the torpedo and set adrift, the charge was carried by the current to Wien, moored about in Vergarola. The charge exploded under the stern, sinking the ship and destroying the human torpedo.
Sinking of the flagship