The League's members were: These Christian states were to have a force of 200 galleys, 100 other ships, 50,000 infantry, 4,500 cavalry and adequate artillery ready by 1 April each year.
John of Austria, illegitimate half-brother of King Philip II of Spain, was designated supreme commander.
Portugal had no forces to spare, owing to its heavy engagement in its own Moroccan campaign, its ongoing maritime confrontations with the Ottomans in the Red Sea and the Indian Ocean, and colonial conflicts with the Malaccan and Johorean Sultanates.
On 7 October 1571, the League won a decisive victory over the Ottoman fleet at the Battle of Lepanto in the Gulf of Patras.
In 1573, the Holy League fleet failed to sail altogether; instead, Don John attacked and took Tunis, only for it to be retaken by the Ottomans in 1574.