On 3 August 1944 three small old merchant ships, overcrowded with about 1,000 Jewish refugees, left the Romanian port of Constanța at about 20:30 hrs.

[4] Armed ships of the Romanian Navy escorted the convoy and provided signal flags to aid their passage from the harbour and through the mined area of the approaches.

On 5 August 1944, about 40 minutes after midnight Mefküre was about 25 miles (40 km) northeast of İğneada in Turkey when flares from an unknown vessel illuminated her.

[11] On 30 July 1944 submarine Shch-215, under command of Captain 3rd Rank AI Strizhak, had departed from Batum, operating at the approaches off Burgas.

This submarine, on the night of 5 August, claimed the sinking of a big schooner with about 200 armed men aboard,[7][9] answering the attack with rifles and light machine guns, and in addition one "barkass", possibly a life boat.