After brief service with the Hungarian People's Republic at the end of the war, she was transferred to the newly created Kingdom of Serbs, Croats, and Slovenes (later Yugoslavia), and renamed Morava.

During the World War II German-led Axis invasion of Yugoslavia in April 1941, Morava was the flagship of the 2nd Mine Barrage Division, and operated on the River Tisza.

[4][6] Her main guns fired a 26 kg (57 lb) armour-piercing, high explosive, shrapnel or fragmentation shell to a maximum range of 8.2 km (5.1 mi) at an elevation of 20°.

[12] On 28 September, Körös, along with the monitor SMS Temes, a patrol boat and a minesweeper, broke through the minefields on the Sava near Belgrade and pushed upstream to join the fighting near Šabac.

[14] The stalemate continued until December 1914 when the Serbs briefly evacuated Belgrade in the face of an Austro-Hungarian assault, although Körös did not support this action.

Körös continued in action against Serbia and her allies at Belgrade until December, when the base of the Danube Flotilla was withdrawn north to Petrovaradin for the winter.

[16] On 22 April 1915, a British picket boat that had been brought overland by rail from Salonika was used to attack the Danube Flotilla anchorage at Zemun, firing two torpedoes without success.

[17] Bulgaria joined the Central Powers in September 1915, and the Serbian Army soon faced an overwhelming Austro-Hungarian, German and Bulgarian ground invasion.

It then escorted a series of munitions convoys down the Danube to Lom, from where they were transferred to the Bulgarian railway system for shipment to the Ottoman Empire.

[20] The position of Romania was uncertain; the Central Powers were aware that the Romanians were negotiating to enter the war on the opposing side of the Entente.

To protect the Danube's 480 km (300 mi) border between Romania and Bulgaria, the flotilla established a sheltered base in the Belene Canal.

This bombardment set fire to oil storage tanks as well as the railway station and magazines, and sank several Romanian lighters.

Flottenabteilung Wulff was sent through the mouth of the Danube and across the Black Sea to Odessa, where it spent several months supporting the Austro-Hungarian troops enforcing the peace agreement with Russia.

[26] In 1932, the British naval attaché reported that Yugoslav ships were engaging in little gunnery training, and few exercises or manoeuvres, due to reduced budgets.

[27] On 6 April 1941, when the World War II German-led Axis invasion of Yugoslavia began, Morava was based at Stara Kanjiža on the Tisza river, as the flagship of the 2nd Mine Barrage Division.

According to her commander, Poručnik bojnog broda[c] Božidar Aranđelović, her crew shot down one German aircraft and captured a Luftwaffe Oberstleutnant.

The three captains conferred, and decided to scuttle their vessels due to the high water levels in the rivers and low bridges, which meant insufficient clearance for the monitors to navigate freely.