Shortly before the Axis invasion of Yugoslavia in April 1941 during the Second World War, she laid minefields along the Dalmatian coast, perhaps inadvertently leading to the sinking of two Yugoslav passenger ships.

During this time she was involved in a gun duel with a surfaced British submarine, in which she was damaged and several of her crew members were killed or wounded.

Her AA armament was further enhanced in 1944 but this did not prevent her from being sunk by British aircraft in September while moored in the port of Vathy on the island of Samos.

Naval authorities determined that a ship was needed to transport seaplanes between the bases and rescue downed aircraft after operations, as had been necessary during World War I.

They decided on the smallest possible ship that would carry supplies and spare parts for ten seaplanes,[1] and the navy placed the order with a German shipyard.

[1] Zmaj's layout was typical for a ship of her type, with the bridge positioned in the center of the raised forecastle, and the aft deck built low and wide to facilitate aircraft handling.

Zmaj's two propellers were powered by a pair of eight-cylinder, four-stroke MAN Diesel engines that had a maximum output of 3,260 shaft horsepower (2,430 kW).

While en route to Yugoslavia the ship had a severe engine room fire on 9 September off Flushing, Netherlands, and was forced to return to Hamburg for repairs.

[1][3] According to the naval historian Zvonimir Freivogel, Zmaj appears to have been little used in her intended role; only her salvage of an upside-down Dornier Wal flying boat in the Bay of Kotor in 1936 has been confirmed.

Following her conversion she made port visits to Piraeus and Istanbul, Turkey, accompanied by the destroyer Dubrovnik and the submarines Hrabri and Smeli.

Zmaj served as the fleet flagship in 1939 and her crew witnessed the new destroyer Ljubljana run aground and sink in January 1940 at the narrow entrance to Šibenik harbor.

Soon after this incident, Zmaj was herself damaged while departing Šibenik harbor when the strong northern bora wind blew her onto rocks, and the squadron commander ordered her anchor dropped.

[10] Shortly before the Axis invasion of Yugoslavia on 6 April 1941 Zmaj,[8] under the command of Captain Leo Zaccaria,[11] laid defensive minefields along the Dalmatian coast and off main ports.

[8] Zmaj was at Šibenik when the invasion began, and was attacked there by Italian Junkers Ju 87B "Picchiatello" dive bombers, but was only slightly damaged.

[8] Drache was recommissioned on 20 August 1942 under Korvettenkapitän Joachim Wünning, and on 6 November was renamed Schiff 50, serving as a troop transport, escort vessel and submarine chaser in addition to her minelaying duties.

On the last of these missions, she was escorting the Romanian steamer Alba Iulia from the Dardanelles to Piraeus when they were attacked by the British submarine HMS Parthian.

After the surrender of Italy in September 1943, she was used to carry troops to capture the Greek island of Kos from a combined British and Italian force on 2–3 October in Operation Eisbär.

The ship was attacked by four British Royal Air Force Bristol Beaufighters off the island of Syros in the Cyclades on 26 September, but incurred only slight damage from their guns.

[17][18][19] Between 12 and 22 December 1943, Schiff 50 participated in two convoys that ferried German troops from Piraeus to the Greek island of Samos, and returned with Italian prisoners of war.

These convoys were escorted by the captured Italian destroyers Turbine and Francesco Crispi (designated Torpedoboot Ausland (foreign torpedo boat)), and renamed TA 14 and TA15 respectively.

Schiff 50 participated in a further troop transport convoy from Piraeus to the island of Milos in the Cyclades on 11 and 12 January 1944, during which she and her escort, the captured Italian destroyer San Martino, now TA17, mistakenly fired on German aircraft.