In 1940, the Caproni Shipyards began construction of the coastal submarines of the “CB” Class, planned for an anti-submarine role in the defense of Italian harbors. These submarines, from the elegant rounded lines, were built in two series and will be used in 1944 and in 1945 from the Decima MAS Flotilla of Italian Social Republic.

displacement: 36/45 tons
length: 15 meters
beam: 3 meters
draft: 2.1 meters
range (diesel): 1,400 miles at 5 knots
range (batteries): 50 miles at 3 knots
power (diesel): 90 hp
power (electric): 100 hp
speed (diesel): 7.5 knots
speed (electric): 7.0 knots
tubes (fwd): two 450mm tubes
crew: two men

In 1942, the first six units of the Regia Marina were initially dispersed to defend the naval base at Taranto, but in May of 1942, these six boats were taken by train to Yalta on the Black Sea to combat the Soviet shipping around Sevastopol. Under command of the IV MAS Flotilla, they sank the Soviet submarines SC-213 (586 tons) and S-32 (840 tons). The only Italian unit lost was CB-5 in the Black Sea.

After the conquest of Sevastopol in August 1942, the five CB units remaining were transferred from Yalta to Costanza, which was a better equipped naval base. In 1943 they are assigned to Decima MAS Flotilla. There they joined with the other small submarines CB-7, CB-8, CB-9, CB-10, CB-11 and CB-12 that defended the port of Taranto. CB-4 has the last success of any Italian submarine when on 28 August 1943, they sank the Soviet submarine SC-207.

On the date of the armistice (8 September 1943), the five CB units in the Black Sea are forfeited to the Kriegsmarine while the boats of the Second CB Squadron are delivered to the Allies in Taranto except for CB-7, which is damaged. It stopped in Pola.

The war is over for the five CB units transferred to the Allies, as they are ignored for the remainder of the war and in 1948, they are broken up for scrap. But for the CB units of the Decima MAS Flotilla, the war continued until the first week in May of 1945.

The Fate of the Five

Right after the signing of the armistice, the five operational CB in the Black Sea were given to the Kriegsmarine and delivered to the Romanian Navy. This was soon changed and on 30 January 1944 they were handed over to the Decima MAS Flotilla of the Italian Social Republic in Sevastopol. They returned & became operational in the spring on 1944. The naval base at Sevastopol was further strengthened by the transfer of men from Bordeaux.

The activity of the submarines of the Decima MAS Flotilla in the Black Sea was limited. In August, Romania was invaded by the Soviet Army and the five boats were scuttled on 25 August 1944 at Costanza as were the six Type II boats of the Kriegsmarine Black See Fleet in the same month.

In the meantime, in the north of Italy, the Decima MAS Flotilla was reorganized by the Italian Social Republic and was again operational. The Squadron ‘Longobardo’ with its CB Class submarines was given the operational zone on the eastern Adriatic Sea on the coasts of Istria, Dalmatia, Veneto and Emilie Romagna.

The Decima Command commissioned the building of fifty new CB units, known as the Second Series. Only ten operational units (CB-13 through CB-22) were delivered and four more (CB-23 through CB-26) were delivered incomplete. Under command of Prince Julio Valerio Borghese, the Decima MAS Flotilla organized two operational bases, both in Istria. These were Pola and in Brioni (Base East), while in Grignano Harbor they formed a support base.

These new bases and new units had newly defined missions – no longer to attack Allied shipping, but to act as ‘mules’ to transport commandoes along the Italian Adriatic coast. The operational situation was obviously quite difficult inasmuch as the Allies had complete air supremacy by then. In March 1944 in an aerial attack on Pola, both CB-14 and CB-15 were lost. The next loss, the third, occurred on 1 October 1944 when the crew of CB-16 mutinied and killed the Commander. The three crewmen aboard beached the boat on the Adriatic beach of Senigallia and then surrendered to the soldiers of VIII Armed Guard.

In the early months of 1945, three more of the CB units were sunk by Allied bombing raids. Then on 11 March 1945, British planes sank CB-22 off the Lussinpiccolo coast – the boat had just been delivered to the Decima MAS Flotilla and this was her first sortie. A week later, on 23 March, CB-13 was sunk and on 3 April, CB-6, formerly CB-17, was badly damaged by American bombs while she was running surfaced off the Cattolica beach. The crew then scuttled the boat, as it was too badly damaged to be repaired.

29 April 1945, the Italian Social Republic surrendered to the Allies and immediately upon learning of this, a German detachment scuttled CB-21. In the following days, the Italian crews abandon their bases with the Germans in pursuit. Only CB-19 succeeded to reach the Venetian coast while CB-18, CB-23, CB-24, CB-25 and CB-26 were scuttled by their crews while en route.

CB-20 had the most unusual fate. She was damaged by German mines while headed to Pola, and the boat was dead in the water and was captured by the Yugoslav Army. After the war, CB-20 was in the service of the Yugoslav Navy, redesignated P901-MALISAN. Stricken from the Navy List in 1950, she was preserved and is in the Museum of Sciences and Technology in Zagabria.

Of the 145 submarines built by Italy for World War II, only the little CB-20 survives today.

VINCENT – many thanks for this great history!

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