The 'Battle of Ist' was a naval engagement in Adriatic Sea fought between French and German ships off the small island of Ist between Skarda and Molat islands (29 February 1944).

The engagement was fought between two Free French destroyers and a German force of two torpedo boat, two corvettes and three minesweepers, which had been deployed to escort a freighter. In the ensuing engagement the French managed to destroy the German freighter and a corvette in return for no loss before withdrawing.

For operations in the Adriatic Sea, in 1944 the Royal Navy formed the 24^th Destroyer Flotilla based at Bari. This flotilla comprised 10 ships, including three French destroyers, namely Le Fantasque, Le Terrible and Le Malin. Under the command of Capitaine de vaisseau Pierre Lancelot, the French ships were to operate in the northern part of the Adriatic Sea while the British would operate farther to the south. The speed of the French destroyers, which were the fastest in the world at the time, allowed them to react swiftly both on intelligence and to strike at targets.

On 29 February the French departed Manfredonia, 50 miles (80 km) to the north of Bari and headed northward through the Adriatic Sea. At the same time a German convoy had departed Pola with a strong escort: the torpedo boats TA-36 and TA-37 (ex-Italian 'Ariete' class Stella Polare and Gladio), the submarine chasers UJ-201 and UJ-205 (ex-Italian 'Gabbiano' class corvettes Egeria and Colubrina) and three small minesweepers. These seven ships were escorting the 6,311-ton freighter Kapitän Diederichsen. The German escorts had been commissioned only recently, and were on only their second operation. The two forces were heading toward each other in the dark of the night with very little moonlight.

At 21.35, on radar, Le Terrible detected possible targets farther to the north and sailed toward them. When the possible target vessels were confirmed as non-Allied, the French opened fire with their 5.5-in (138.6-mm) main guns at a range of about 9,000 yards (8230 m) just to the west of Ist island, taking the Germans by complete surprise. Le Malin opened fire on the largest of the targets, which was the freighter, and soon scored a hit. The Germans attempted to lay a smokescreen, but the destroyers exploited their speed advantage and soon closed using their radar. Le Terrible scored more hits on the freighter while Le Malin targeted the closest of the escorts. At 4,500 yards (4115 m) Le Terrible fired two salvoes of 21.7-in (550-mm) torpedoes: the initial salvo missed, but the first weapon of the second salvo hit the freighter amidships, and the German ship quickly caught fire and lost propulsion to drift helplessly.

Meanwhile, UJ-201 had been struck by Le Malin's well-directed 90-lb (40.8-kg) shells. Now well ranged, the German corvette was hit six more times and was soon a burning wreck. Le Malin was close enough to launch a salvo of torpedoes: one of the weapons struck and detonated the ship’s magazine causing a tremendous explosion, and the ship sank immediately with all hands. Both Le Terrible and Le Malin then took on the other German escorts. TA-36 suffered near misses and was soon hit in the bow, suffering light damage. However, TA-37 was hit in the engine room, burst into flames and caused a rapid loss of speed. Lancelot was about to finish the German ship, but on seeing low fast-moving silhouettes of possible Schnellboote decided to withdraw. The silhouettes were in fact those of the motor minesweepers arriving to help with the crew of the stricken freighter and search for survivors of the destroyed UJ-201. Lancelot ordered the two French destroyers to head back to port.

Kapitän Diederichsen remained afloat, but only for a short time. An attempt to take her in tow failed and the survivors were taken off by the German escorts. The heavily damaged TA-37 was towed to Pola.

The French forced remained in the Adriatic Sea for half of the year in tasks such as the bombardment of German positions on the island of Zante, and on 19 March sank two Siebel ferries (SF-273 and SF-274 on their way to Pylos, and crippled another two. In August the French warships took part in 'Dragoon', the Allied invasion of southern France.