By late 1941, the British had broken the Italian naval cipher and were using the intelligence, codenamed Ultra, to devastating effect. Force K, operating from Malta, had destroyed convoy after convoy, cutting off supplies to Rommel's forces in Libya. In November alone, nearly 70 percent of all supplies sent to Libya were lost, including 92 percent of the fuel. Without aviation fuel, Axis aircraft could not fly, and without air cover, more convoys would be destroyed. The Italian naval command, Supermarina, hit upon a desperate solution: load the fast light cruisers Da Barbiano and Di Giussano with fuel and send them racing across the Mediterranean to Tripoli. The ships belonged to the 4th Cruiser Division under Admiral Antonino Toscano, and they were fast enough -- in theory -- to outrun any threat.

The cruisers sailed from Palermo on the evening of 12 December, loaded with aviation fuel, gasoline, naphtha, food, and 135 naval personnel being transferred to Tripoli. The fuel barrels were stacked on the stern of Da Barbiano so thickly that the aft gun turrets were completely blocked. Toscano and his officers acknowledged the problem at a pre-departure briefing: if enemy ships appeared, the barrels would have to be thrown overboard before the guns could fire. A third cruiser, Bande Nere, was supposed to join but broke down, and her cargo was transferred to the other two ships, making them even more heavily loaded. Their sole escort was a single torpedo boat; a second had also broken down. The Italians had already attempted this run three days earlier but turned back after being spotted by British reconnaissance. Supermarina criticized Toscano for aborting that mission. This time, he pressed on.

Unknown to the Italians, four destroyers of the British 4th Destroyer Flotilla -- Sikh, Legion, Maori, and the Dutch Isaac Sweers -- were transiting eastward through the Mediterranean, heading from Gibraltar to Alexandria. British codebreakers had decrypted Italian signals about the supply run, and the destroyers were redirected to intercept. A radar-equipped Wellington bomber located the Italian ships and guided the destroyers in. At 3:15 AM on 13 December, Toscano suddenly reversed course -- a decision never fully explained. The maneuver threw his own formation into confusion. Minutes later, the Allied destroyers appeared from astern, hugging the shoreline where the dark mass of Cape Bon hid them from Italian lookouts. Sikh and Legion launched torpedoes at Da Barbiano from nearly point-blank range. The first torpedo struck below the forward turret. Machine gun fire raked the deck, igniting the fuel barrels. A second torpedo hit the engine room. The burning fuel spilled into the sea.

Da Barbiano capsized and sank at 3:35 AM, just twenty minutes after the first torpedo hit. Admiral Toscano, Captain Rodocanacchi, and 534 members of the crew went down with the ship in a sea already burning with spilled aviation fuel. Maori and Isaac Sweers had turned their fire on Di Giussano, which managed only three salvoes before being disabled by torpedoes and gunfire. Her crew fought to keep her afloat, but fires raged out of control and she broke in two, sinking at 4:20 AM with the loss of 283 men. In total, approximately 817 Italian sailors died -- 534 from Da Barbiano and 283 from Di Giussano. The torpedo boat Cigno rescued nearly 500 survivors, and another 145 were later picked up by Italian motor torpedo boats. The four Allied destroyers sailed away into the night without a scratch. The fuel that was supposed to keep Axis aircraft flying over Libya instead burned on the surface of the Mediterranean, visible for miles.