his flagship, Viribus Unitis, and Prinz Eugen south with the lead elements of his fleet. On the evening of 9 June, Szent István and Tegetthoff followed along with their own escort ships. Horthy's plan called for and to engage the Barrage with the support of the Tátra-class destroyers. Meanwhile, Admiral Spaun and would be escorted by the fleet's four torpedo boats to Otranto to bombard Italian air and naval stations. The German and Austro-Hungarian submarines would be sent to Valona and Brindisi to ambush Italian, French, British, and American warships that sailed out to engage the Austro-Hungarian fleet, while seaplanes from Cattaro would provide air support and screen the ships' advance. The battleships, and in particular the Tegetthoffs, would use their firepower to destroy the Barrage and engage any Allied warships they ran across. Horthy hoped that the inclusion of these ships would prove to be critical in securing a decisive victory. En route to the harbour at Islana, north of Ragusa, to rendezvous with Viribus Unitis and Prinz Eugen for the coordinated attack on the Otranto Barrage, Szent István and Tegetthoff attempted to make maximum speed in order to catch up to the rest of the fleet. In doing so, Szent Istváns turbines started to overheat and speed had to be reduced to . When an attempt was made to raise more steam in order to increase to Szent István produced an excess of smoke. At about 3:15 am on 10 June, two Italian MAS boats, MAS-15 and MAS-21, spotted the smoke from the Austrian ships while returning from an uneventful patrol off the Dalmatian coast. The MAS platoon was commanded by Capitano di corvetta Luigi Rizzo, who had sunk the Austro-Hungarian coastal defense ship in Trieste six months before. The individual boats were commanded by Capo timoniere Armando Gori and Guardiamarina di complemento Giuseppe Aonzo respectively. Both boats successfully penetrated the escort screen and split to engage each of the dreadnoughts. MAS-21 attacked Tegetthoff, but her torpedoes failed to hit the ship. MAS-15 fired her two torpedoes successfully at 3:25 am at Szent István. Both boats evaded any pursuit although MAS-15 had to discourage the Austro-Hungarian torpedo boat Tb 76 T by dropping depth charges in her wake. Tegetthoff, thinking that the torpedoes were fired by submarines, pulled out of the formation and started to zigzag to throw off any further attacks. She repeatedly fired on suspected submarine