The passenger ship Regele Carol I was build in Glasgow, England, between 1897-1898, and arrived in Romania on 28 June 1898, entering service with the Serviciul Maritim Roman (SMR). It operated on the Constanta-Istanbul and Constanta-Piraeus routes. In 1899, Carol's burners were adapted to burn fuel oil instead of coal, and in 1905 a wireless telegraph post was set up on the ship. As Romania entered the First World War, in 1916 Carol was put at the allied Imperial Russian Navy's disposal.

In October 1916, at Sevastopol, Carol was turned into an auxiliary cruiser. Four 101 mm guns, two 63 mm AA guns, two search-lights and installations for carrying and operating two seaplanes. In March 1917 it was part of the Russian cruiser division, which bombed the Anatolian coast and guarded the Bosphorus. Following the start of the Russian Revolution, Carol was seized by Caucasian Socialist Republic at Batumi, but managed to escape with the help of the Russian officers onboard and arrived at Sulina on 31 March/13 April 1918. The Romanian government agreed to return the guns to the Russians.

After the First World War ended, Carol was returned to its civilian life as a passenger ship, following the Constanta-Varna-Istanbul-Salonika route, and, after the beginning of the Second World War and the entering of Italy in war, the Constanta-Istanbul route. In 1941, the need for minelayers caused the requisition of Carol, whose main deck accepted mine mounts. Commander of the ship was appointed Lieutenant Commander Ion Borcea. Between 16 and 19 June 1941, Carol laid mines along Romanian coast, between Cape Midia and Tuzla, together with NMS Amiral Murgescu. These barrages did their duty on 26 June 1941, when they sunk the Soviet destroyer Moskva and damaged the cruiser Voroshilov.

On 25 July 1941 two 20 mm AA guns were mounted on board, and days later, two 105 mm guns.

On 6 October 1941, under the command of Lieutenant Commander Florian Popescu, Carol laid anti-submarine mines in the southern part of Midia-Tuzla barrage, together with the NMS Amiral Murgescu and NMS Dacia mine laying ships, during Operation Varna. On 9 October 1941, Carol laid anti-submarine mines south-west of Cape Kaliakra. On 10 October 1941, at 11:50 hours, after having left Varna harbor with a new load of mines, Carol hit a mine and sunk in 13 minutes, 2 miles away of Galata Burnu lighthouse. The mine was part of a barrage laid by the L-4 Soviet submarine, in the previous month. One NCO and 20 seamen lost their lives, the rest being rescued by the torpedo boat Smeul, which was convoying Carol.

Even though the NMS Regele Carol I sank in October, the mine barrages it had laid in 1941 continued to make victims. The same month, the Soviet submarine M-58 hit a mine in front of Constanta. On 30 November 1941, Sc-211, while was trying to attack a convoy made up of the Romanian cargo ship Carpati and the Bulgarian Czar Ferdiannd, entered a barrage laid on 8 October and sank near Varna. Sc-204 had the same fate also near Varna in December 1941. One year later, in December 1942, the L-24 submarine hit a mine from the S-15 barrage and sank near the Kaliakra Cape.

Specifications

Displacement	3600t
Length	106.7m
Width	10.37m
Draft	5m
Guns	2 x 105mm 2 x 20mm
Mines	200
Engine type	6500 hp
Max speed	18 knots
Crew	80