At 17.25 hours on 30 December 1944, U-956 attacked convoy KP-24 near Skorobeevskaja Guba (Rybachij peninsula) only a few hours after its departure and reported one ship sunk and another probably sunk. However, only the Tbilisi (Master V.K. Subbotin) which carried 124 military personnel of the 14th Army was torpedoed. Two men died when the bow broke off and sank shortly afterwards. The cargo in the stern caught fire and due to panic some passengers and crew members jumped overboard and drowned or died of exposure. The Soviet submarine hunter BO-217 tried to get alongside of the torpedoed ship but was not able to do so due to high seas and heavy winds. About 18.00 hours, the Soviet submarine hunter BO-150 began picking up survivors from the water and rescued 60 men. About three hours after the attack, the submarine hunters were ordered to return to base because of the weather, only the Soviet minesweepers T-113 and T-115 remained near the torpedoed ship. At 01.00 hours on 31 December, T-115 took off the remaining survivors but when her master left the ship as last man, he fell overboard and was crushed between the ships.

At 02.00 hours, the Soviet destroyers Zhestkij and Zhivuchij left their base and later tried to take the Tbilisi in tow, but failed in the bad weather and guarded the ship until the Soviet tugs M-2 and M-12, escorted by a minesweeper and a submarine hunter, arrived at 12.00 hours on 1 Jan 1945. In about 11 hours, the tugs towed the ship to Teriberka and on 5 January continued to Murmansk. The Tbilisi was not repaired until 1959, when the bow of the wreck of Horace Gray was fitted to the vessel at the Krasnaia Kuznitza shipyard in Archangelsk. She was scrapped in 1977.