At the start of the April 1941 Axis invasion of Yugoslavia, two boats managed to escape to Alexandria in Egypt where they served under the operational command of the British Mediterranean Fleet and under the administrative control of the Yugoslav government-in-exile.

They were also used by the Italians as the model for the Italian-built CRDA 60 t motor torpedo boats and the submarine chasers of the VAS class.

Another was damaged by its crew, but captured and repaired by the Germans and transferred to the National Republican Navy of the Italian Social Republic for use as a harbour defence vessel at Venice.

They served as part of the 24th S-Boat Flotilla, largely in the Aegean Sea, until they were finally stricken at Salonika in September 1944 as the Germans withdrew from Greece.

Thus, in 1926, the KM had ordered two MTBs based on John I. Thornycroft & Company's existing class of 55-foot-long (17 m) Coastal Motor Boats from the United Kingdom.

[4] In the mid-1930s, the Yugoslav government sought to improve relations with Italy and Germany to create new economic opportunities for the country.

In 1936 the KM ordered eight MTBs (Serbo-Croatian Latin: motorna torpiljarka) that were to be built by the Lürssen shipyard in Vegesack, Germany, based on the existing German design of the S–2 class.

[6] The Orjen-class boats were an improved version of the S–2 class, designed with round-bilged displacement hulls which combined a high degree of seaworthiness with strength and light weight thanks to their composite construction using wood and steel.

The double hull was constructed of mahogany arranged diagonally over steel frames, unlike the light alloy used in the original S-2 boats.

[10] Together, the three engines were rated at between 2,850–3,000 brake horsepower (2,130–2,240 kW), giving the boats a maximum speed of 34 knots (63 km/h; 39 mph).

A six-cylinder Maybach S5 auxiliary cruising engine rated at 100 bhp (75 kW) was coupled to the central shaft with a chain, and powered the boats to a maximum speed of 7 kn (13 km/h; 8.1 mph).

The boats carried the French 533 mm (21 in) torpedo, which was launched by a combination of compressed air and an explosive charge.

[13] For anti-aircraft defence a single Bofors 40 mm (1.6 in) gun was mounted on the aft deckhouse,[2][11][12] for which 200 rounds were carried aboard.

Diplomatic pressure resulted in faster production, but the last torpedoes were only delivered immediately prior to the outbreak of World War II on 1 September 1939.

[11] On 8 April, the combined 2nd and 3rd Torpedo Divisions were tasked to support an attack on the Italian enclave of Zara (Zadar) on the Dalmatia coast,[11] which the Yugoslav High Command feared would be used as a bridgehead during the invasion.

[11][16][19] The following day the crews became aware that a general Yugoslav surrender was imminent, and they were ordered not to provoke the invading forces.

By 17 April, the complete collapse of Yugoslav defences and the general surrender were imminent, prompting Kern to lead Durmitor, Kajmakčalan, Triglav and Dinara out of the Bay of Kotor that day.

A fire in Triglav's engine room – sabotaged by one of her officers – caused her to turn back, and Dinara sailed to her assistance.

[11] Elsewhere in the Bay of Kotor, Milan Spasić and Sergej Mašera died blowing up the destroyer Zagreb to prevent her from falling into enemy hands.

[22] Kern sailed on with the two remaining boats, Durmitor and Kajmakčalan, loaded with personnel who wanted to continue the fight, including crew members from Velebit, Triglav and Orjen, the harbour defence ship Dalmacija and the tug Jaki.

They managed to avoid detection by the Italian observation post on the island of Saseno near the Albanian port of Valona.

[23] The two boats were first tasked with patrolling the outside of the harbour in anticipation of an attack by Axis coastal craft,[24] and also escorted small convoys in the area.

[23] Between September 1941 and March 1942 the two boats underwent a refit at Port Said, where they were also fitted with ASDIC and their crews were trained for anti-submarine work.

This was followed by more than a year of convoy escort duty between Alexandria, Mersa Matruh and Port Said, and on at least one occasion they engaged enemy aircraft.

[33] They formed part of the 24th S-Boat Flotilla,[34] which was to consist of nine captured MTBs, including the five remaining Orjen-class boats.

[11] In December 1943, MS 41 was transferred to the National Republican Navy of the Italian Social Republic, the fascist rump puppet state in northern Italy that was established by the Germans after the armistice.

The following day she transported 20 German soldiers and towed the artillery lighter MAL12 to Oxeia to assist with mopping-up operations, but by the time they arrived, the enemy was gone.

[34][36] On 27 September 1944 MS 41/S 605 struck a mine near Porto Corsini – the harbour of Ravenna – and sank the following day during a gale off the mouth of the Montone River, with seven of her crew lost.