Italian MAS continued to be improved after the end of World War I, thanks to the availability of
Isotta Fraschini engines. The MAS of World War II had a maximum speed of and mounted two torpedoes and one
Breda 13.2 mm machine-gun. Isotta-Fraschini produced its ASM 180 series of marine engines for the MAS from 1933 to 1955. The standard engine in World War II was the ASM 184, a 18-cylinder machine capable of producing with 2,000 rpm. In 1940 there were 48 MAS 500-class units available. Older units were used in secondary theatres, such as the
Italian East Africa. Notable war actions performed by MAS include the torpedoing of the Royal Navy
C-class cruiser by
MAS 213 of the 21st MAS Squadron working within the
Red Sea Flotilla off
Massawa,
Eritrea; and the failed
Raid on Grand Harbour of Malta in July 1941, which caused the loss of two motorboats
, MAS 451 and
MAS 452, the latter recovered by the British, put in service as a
tender and renamed
XMAS. Five MAS were scuttled in Massawa in the first week of April 1941 as a part of the Italian plan for
the wrecking of Massawa harbor in the face of the British advance.
MAS 204,
206,
210,
213, and
216 were sunk in the harbor; four of the boats were in need of mechanical repairs and could not be evacuated. On 24 July 1941, amid heavy fire from the escorts,
MAS 532 torpedoed and crippled the transport
Sydney Star, escorted by the destroyer and part of the
Operation Substance (Convoy GM 1). The steamer managed to limp to Malta assisted by the destroyer
HMAS Nestor. On 1 December 1941, two Italian MAS boats engaged with torpedoes and machine gun fire the
Soviet icebreaker
Anastas Mykoyan, en route from the
Dardanelles to
Suez, forcing it to run aground on the
Turkish coast off
Kastelorizo. Even though the Soviet vessel was refloated and reached
Haifa for repairs the next day, the action compelled the Turkish government to intern eight Soviet ships set to repeat the same journey. Also in the Aegean Sea, on 27 April 1942, near Kastelorizo, a flotilla of MAS rescued a motor sailing boat with Jewish refugees from
Romania. On 15 March 1943, MAS
545 and
559 seized the Greek motor sailing ship
Aghios Dimitros, which had been taken over by a British Army boarding party from the Greek submarine
Papanicolos and was being rerouted to Turkish waters. The small vessel was carrying German ammunition. The British crew and a Greek naval officer were taken prisoner.
MAS 554,
554 and
557 sank three allied freighters on the night of 13 August 1942 off
Cape Bon, in the course of
Operation Pedestal, for a total tonnage of 48,500 tons. On 29 August 1942, a smaller type of MAS boat, the
MTSM, torpedoed the British destroyer
Eridge off El Daba,
Egypt, disabling it for the remainder of the war. in June 1942, during the
Siege of Leningrad A flotilla of MAS served at German request as reinforcements in the
Black Sea for the planned attack on
Sevastopol in June 1942. The MAS squadron came under intense air attack from Soviet
fighter-bombers and torpedo boats but performed well. They sank the 5,000-ton steamer
Abkhazia and disabled the 10,000-ton transport
Fabritius, which was subsequently destroyed by German
Stuka dive-bombers. MAS boats destroyed troop barges and damaged Soviet warships. A MAS boat commander, Sub-Lieutenant Ettore Bisagno, was killed in battle. One MAS was destroyed and three damaged by fighter-bombers in September 1942 during a heavy attack on
Yalta. In the early hours of 3 August 1942, three MAS boats torpedoed and disabled the
Soviet cruiser Molotov south-west of
Kerch. In May 1943, the seven MAS boats in the Black Sea were transferred to the
Kriegsmarine. In August that year, they were transferred to the
Romanian Navy. These seven boats were wooden-hulled, each displacing 25 tons. Top speed amounted to 42 knots, generated by petrol engines powering two shafts. They were armed with one 13 mm heavy machine gun or one 20 mm anti-aircraft gun, 6 depth charges and two 450 mm torpedoes. Another flotilla of four MAS, the
XII Squadriglia MAS, was deployed to
Lake Ladoga in April 1942 to support the
siege of Leningrad. They claim the sinking of a Soviet gunboat of the Bira class, a 1,300-ton cargo ship and several barges. Soviet sources say that the gunboat, the
Selemdzha, was only lightly damaged when the torpedo exploded in the lake's bottom, with two wounded on board. After the signing of the
Cassibile agreement, MAS boats sank the German torpedo boat
TA11 (ex French ''L'Iphigénie'') at
Piombino, on 11 September 1943. The
obsolescence of small MAS became apparent during the conflict, and they were increasingly replaced by larger Yugoslavian
E-boats built in Germany and by new improved versions, classified
"MS" (Moto Siluranti) by the
Regia Marina. A type of anti-submarine craft based on the MAS design was developed by the Italian Navy in World War II. This was the
vedetta anti sommergibile, or "VAS", equipped with a good amount of
anti-submarine warfare equipment given her small size. ==Cultural legacy==