After failed negotiations with Germany and Austria-Hungary over Italy joining the war as a member of the Central Powers, the Italians negotiated with the Triple Entente for Italy's eventual entry into the war on their side in the Treaty of London, signed on 26 April 1915. On 4 May Italy formally renounced her alliance to Germany and Austria-Hungary, giving the Austro-Hungarians advanced warning that Italy was preparing to go to war against them. On 20 May, Emperor Franz Joseph I gave the Austro-Hungarian Navy authorization to attack Italian ships convoying troops in the Adriatic or sending supplies to Montenegro. Haus meanwhile made preparations for his most valuable battleships to sortie out into the Adriatic in a massive strike against the Italians the moment war was declared. On 23 May 1915, between two and four hours after the Italian declaration of war reached the main Austro-Hungarian naval base at Pola, the Austro-Hungarian fleet, including the three ships of the "Tegetthoff" class, departed to bombard the Italian coast.