She entered KM service in November 1939, was armed with a main battery of four Škoda 120 mm (4.7 in) guns in superfiring single mounts – two forward and two aft of the superstructure – and she had a practical top speed of 35 knots (65 km/h; 40 mph).
In 1940, Ljubljana ran aground on a reef off the Yugoslav port of Šibenik and sank due to the serious damage caused to her hull.
Yugoslavia entered World War II when the German-led Axis powers invaded in April 1941, and Ljubljana – still under repair – was captured by the Italians.
The endurance requirement reflected Yugoslav plans to deploy the flotilla leaders to the central Mediterranean, where they would be able to operate alongside French and British warships.
Soon after she was ordered, the onset of the Great Depression and attendant economic pressures meant that only one ship of the planned half-flotilla was ever built.
In 1934, the KM decided to acquire three smaller destroyers to operate in a division led by Dubrovnik, leading to the building of the Beograd class.
The lower sections of the funnels were inside the superstructure in the midsection of the ship aft of the forecastle, which also housed the boiler room access and some offices.
[8] She carried 120 tonnes (120 long tons) of fuel oil,[8] in nine bunkers located on either side of the boiler rooms and in the double bottom directly below the bridge.
[7] The initial intention to arm the class with four Czechoslovak-built Škoda 140 mm (5.5 in) L/56[a] guns – as carried by Dubrovnik – was quickly dropped, as they were too heavy for the smaller destroyers.
[19] Soon after commissioning, Ljubljana participated in an anti-submarine warfare exercise in the passages between the large islands of Mljet and Korčula off the Dalmatian coast on 23 January 1940.
The exercise included both her sister ships, and the following day the division sailed towards Šibenik for a port visit to familiarise the population with the new destroyers.
The resulting naval court of inquiry led to the early retirement of almost the entire staff of the Yugoslav fleet headquarters.
[20] During one attempt, hydraulic cylinders borrowed from the Royal Italian Navy came free when the tow cable parted, and floated away to be collected by Dubrovnik.
On the night of 29 February/1 March, the Italian ocean liner SS Leonardo da Vinci accidentally struck the submerged Ljubljana, further damaging her rudder and propellers.
[24] However, her first identified escort was of the captured Greek tanker Patrakis Nomikos – of 7,020 gross register tons (GRT) – from Brindisi in southern Italy to Patras in western Greece in late November 1942.
[21] From 9 February to 22 March 1943, Lubiana participated in a series of troop transport convoys for the German and Italian armies in North Africa.
[21] In bad visibility and poor weather, Lubiana's crew made a navigational error, and along with Le Borgne and Aquila she was grounded at about 04:00 on 1 April, approximately 1.6 kilometres (1 mi) east of Ras El Ahmar – about 8 nmi (15 km; 9.2 mi) west of the Cap Bon Peninsula – while entering the Gulf of Tunis.
Due to heavy seas and adverse weather, it was impossible to salvage Lubiana, and she was abandoned, wrecked on the rocks, and declared a total loss.