The Adriatic campaign of World War II was a minor naval campaign fought during World War II between the Greek, Yugoslavian and Italian navies, the Kriegsmarine, and the Mediterranean squadrons of the United Kingdom, France, and the Yugoslav Partisan naval forces. Considered a somewhat insignificant part of the naval warfare in World War II, it nonetheless saw interesting developments, given the specificity of the Dalmatian coastline.
Prelude – Italian invasion of Albania
On 7 April 1939, Mussolini's troops occupied Albania, overthrew King Zog, and annexed the country to the Italian Empire. Naval operations in the Adriatic consisted mostly of transport organisation through the ports of Taranto, as well as coastal bombardment in support of the landings on the Albanian coast. The Italian naval forces involved in the invasion of Albania included the battleships Giulio Cesare and Conte di Cavour, three heavy cruisers, three light cruisers, nine destroyers, fourteen torpedo boats, one minelayer, ten auxiliary ships and nine transport ships. The ships were divided into four groups, which carried out landings at Vlorë, Durrës, Sarandë and Shëngjin.
When Italy entered World War II, on 10 June 1940, the Italian Navy's main naval bases in the Adriatic Sea were Venice, Brindisi, and Pola. The northern Adriatic was under the jurisdiction of the Northern Adriatic Autonomous Naval Command, headquartered in Venice and commanded by Vice Admiral Ferdinando of Savoy (replaced by Admiral Emilio Brenta shortly before the armistice with the Allies); the southern Adriatic was under the jurisdiction of the Southern Adriatic Naval Command, headquartered in Brindisi and commanded by Admiral Luigi Spalice. Vice Admiral Vittorio Tur was the naval commander of Albania, with headquarters in Durrës. Naval commands also existed in Pola (home of the Italian Navy's submarine school) and Lussino.
Italian naval forces in the Adriatic, at the outbreak of the war, included the destroyers Carlo Mirabello and Augusto Riboty and the 7th Torpedo Boat Squadron (Angelo Bassini, Nicola Fabrizi, Enrico Cosenz and Giacomo Medici) in Brindisi, the 15th Torpedo Boat Squadron (Palestro, Confienza, San Martino and Solferino) in Venice, the gunboat Ernesto Giovannini in Pola, the 2nd MAS Squadron (four boats) in Pola, the 3rd MAS Squadron (two boats) in Brindisi, and several minelayers (the relatively shallow waters of the Adriatic Sea were particularly favourable for mine warfare). Seven submarines were based in Brindisi: Balilla, Domenico Millelire, Enrico Toti, and Antonio Sciesa (belonging to the 40th Submarine Squadron), Brin (of the 42nd Squadron), Anfitrite (44th Squadron) and Ondina (48th Squadron).
Greco-Italian War
The Greco-Italian War lasted from 28 October 1940 to 30 April 1941 and was part of World War II. Italian forces invaded Greece and made limited gains. At the outbreak of hostilities, the Royal Hellenic Navy was composed of the old cruiser Georgios Averof, 10 destroyers (four old Thiria class, four relatively modern Dardo class and two new Greyhound class), several torpedo boats and six old submarines. Faced with the formidable Regia Marina, its role was primarily limited to patrol and convoy escort duties in the Aegean Sea. This was essential both for the completion of the Army's mobilization and the overall resupply of the country, the convoy routes being threatened by Italian aircraft and submarines operating from the Dodecanese Islands. Nevertheless, the Greek ships also carried out limited offensive operations against Italian shipping in the Strait of Otranto.
On the Italian side, convoy operations between Italy and Albania were under the responsibility of the High Command for Traffic with Albania (Comando Superiore Traffico Albania, Maritrafalba), established in Valona on 5 October 1940 and initially held by Captain Romolo Polacchini. Maritrafalba's forces included two elderly Mirabello-class destroyers, eleven equally old torpedo boats (belonging to the Palestro, Curtatone, Sirtori, Generali and La Masa classes), four more modern Spica-class torpedo boats of the 12th Torpedo Boat Squadron, four auxiliary cruisers and four MAS of the 13th MAS Squadron. The main Italian supply routes were from Brindisi to Valona and from Bari to Durrës.
Greek destroyers carried out three bold but fruitless night-time raids (14–15 November 1940, 15–16 December 1940 and 4–5 January 1941). The main Greek successes came from the submarines, which managed to sink some Italian transports (Greeks also lost a submarine in the process), but the Greek submarine force was too small to be able to seriously hinder the supply lines between Italy and Albania; between 28 October 1940 and 30 April 1941 Italian ships made 3,305 voyages across the Otranto straits, carrying 487,089 military personnel (including 22 field divisions) and 584,392 tons of supplies while losing overall only seven merchant ships and one escort ship. Although the Regia Marina suffered severe losses in capital ships from the British Royal Navy during the Taranto raid, Italian cruisers and destroyers continued to operate covering the convoys between Italy and Albania. Also, on 28 November, an Italian squadron bombarded Corfu, while on 18 December and 4 March, Italian naval units shelled Greek coastal positions in Albania.
The only surface engagement between the Regia Marina and the Royal Navy occurred on the night of 11–12 November 1940, when a British squadron of three light cruisers and two destroyers attacked an Italian return convoy consisting of four merchant ships escorted by the auxiliary cruiser Ramb III and the torpedo boat Nicola Fabrizi, in the Battle of the Strait of Otranto. All four merchants were sunk, and Nicola Fabrizi was heavily damaged. In March 1941, Fairey Swordfish torpedo bombers of the Fleet Air Arm, based in Paramythia, Greece, raided the harbour of Valona multiple times, sinking one merchant ship, one torpedo boat and the hospital ship Po; the Regia Aeronautica then discovered the air base and bombed it, knocking it out for some weeks. In April the air field became operational again and another raid on Valona was carried out, sinking two additional merchant ships; on the same day, however, German forces launched their invasion of Greece, and the base at Paramythia was bombed by the Luftwaffe and permanently destroyed.
Invasion of Yugoslavia
The Invasion of Yugoslavia (also known as Operation 25) began on 6 April 1941 and ended with the unconditional surrender of the Royal Yugoslav Army on 17 April. The invading Axis powers (Nazi Germany, Fascist Italy and Hungary) occupied and dismembered the Kingdom of Yugoslavia.
When Germany and Italy attacked Yugoslavia on 6 April 1941, the Yugoslav Royal Navy had available three destroyers, two submarines and 10 MTBs as the most effective units of the fleet. One other destroyer, the Ljubljana, was in dry-dock at the time of the invasion and she and her anti-aircraft guns were used in defence of the fleet base at Kotor. The remainder of the fleet was useful only for coastal defence and local escort and patrol work.
Kotor (Cattaro) was close to the Albanian border and the Italo-Greek front there, but Zara (Zadar), an Italian enclave, was to the north-west of the coast, and to prevent a bridgehead being established, the Beograd, four of the old torpedo boats and six MTBs were despatched to Šibenik, 80 km to the south of Zara, in preparation for an attack. The attack was to be co-ordinated with the 12th "Jadranska" Infantry Division and two Odred (combined regiments) of the Royal Yugoslav Army attacking from the Benkovac area, supported by air attacks by the 81st Bomber Group of the Royal Yugoslav Air Force.
The Yugoslav forces launched their attack on 9 April, but by 13 April Italian forces under General Vittorio Ambrosio had counter-attacked, and were in Benkovac by 14 April. The naval prong of the attack faltered when Beograd was damaged by near misses from Italian aircraft off Šibenik. With her starboard engine put out of action, she limped to Kotor, escorted by the remainder of the force, for repair. Italian air raids on Kotor badly damaged the minelayer Kobac, which was beached to prevent sinking.
The maritime patrol float-planes of the Royal Yugoslav Air Force flew reconnaissance and attack missions during the campaign, as well as providing air cover for mine-laying operations off Zara. Their operations included attacks on the Albanian port of Durrës, as well as strikes against Italian re-supply convoys to Albania. On 9 April, one Dornier Do 22K floatplane notably took on an Italian convoy of 12 steamers with an escort of eight destroyers crossing the Adriatic during the day, attacking single-handed in the face of intense AA fire. No Italian ships, however, were sunk by Yugoslav forces; an Italian tanker was claimed damaged by a near miss off the Italian coast near Bari. Most of the small Yugoslav fleet (the old cruiser Dalmacija, three destroyers, six torpedo boats, three submarines, eleven minelayers, and several auxiliary ships) was seized by Italian ground forces in its bases at Split and Kotor, and later recommissioned under Italian flag. Only four Yugoslav ships escaped capture: the submarine Nebojsa and two motor torpedo boats sailed to Allied-controlled ports, while the Zagreb was scuttled to prevent capture.
Italian occupation and Yugoslav resistance
After the invasion, Italy controlled the entire eastern Adriatic coast through the annexation of much of Dalmatia, the Italian occupation zone of the Independent State of Croatia, the Italian governorate of Montenegro, and the Italian puppet regime of the Albanian Kingdom (1939–1943).
Naval forces of the Yugoslav Partisans were formed as early as 19 September 1942, when Partisans in Dalmatia formed their first naval unit made of fishing boats, which gradually evolved (especially after the armistice between Italy and the Allies) into a force able to conduct complex amphibious operations. This event is considered to be the foundation of the Yugoslav Navy. At its peak during World War II, the Yugoslav Partisans' Navy commanded nine or 10 armed ships, 30 patrol boats, close to 200 support ships, six coastal batteries, and several Partisan detachments on the islands, around 3,000 men.
After the Italian capitulation of 8 September 1943, following the Allied invasion of Italy, the Partisans took most of the coast and all of the islands. On 26 October, the Yugoslav Partisans' Navy was organized first into four, and later into six Maritime Coastal Sectors (Pomorsko Obalni Sektor, POS). The task of the naval forces was to secure supremacy at sea, organize defense of coast and islands, and attack enemy sea traffic and forces on the islands and along the coasts.
British submarine activity
After the fall of Greece and Yugoslavia, the complete Italian control of both coasts of the Adriatic, and the distance from British naval and air bases, meant the end of all British air and surface operations in the Adriatic Sea. From the spring of 1941 to September 1943, Royal Navy activity in the Adriatic was thus limited to submarine operations, mainly in the Southern Adriatic; Italian convoys across the Adriatic suffered negligible losses. Between June 1940 and September 1943, only 0,6 % of the personnel and 0,3 % of the supplies shipped from Italy to Albania and Greece were lost; two-thirds of these losses were caused by submarines, mostly British. Four Royal Navy submarines were lost in the Adriatic, most likely to mines. British surface ships re-entered the Adriatic after the September 1943 armistice, when the much weaker Kriegsmarine forces remained the only opponent.
German occupation
As a first move (Operation Wolkenbruch) the Germans rushed to occupy the northern Adriatic ports of Trieste, Rijeka and Pula, and established the Operational Zone Adriatic Coast (OZAK), with its headquarters in Trieste, on 10 September. It comprised the provinces of Udine, Gorizia, Trieste, Pula (Pola), Rijeka (Fiume) and Ljubljana (Lubiana). Since an Allied landing in the area was anticipated, OZAK also hosted a substantial German military contingent, the Befehlshaber Operationszone Adriatisches Küstenland commanded by General der Gebirgstruppe Ludwig Kübler. On 28 September 1944, these units were redesignated XCVII Armeekorps. Soon, German marine units were also formed. Royal Navy engagement was also on the rise.