After having been refused a personal meeting, Richard sends a Moroccan prisoner to Saladin's camp as a sign of goodwill. Finally, Saladin accepts a three-day truce and allows his younger brother, Al-Adil, to negotiate with Richard. June 25 – The Crusader armies (now totaling some 25,000 men) who are deployed around Acre, implement a unified strategy of assault-based siege. Teams of sappers and, increasingly massive use of advanced and new stone-throwing catapults, brought by Philip II and Richard I, are used to hammer Acre's walls continuously with giant, accurately loosed stones. By late June, the assault is beginning to undermine the walls, which are tottering. Because of troop shortages and disease, the Muslim defenders can not any longer strengthen their walls. July 3 – The Crusaders change their strategy from battering the Acre fortifications to exploiting the breaches. After only the first day of these all-out attacks to seize the city, Saladin's governor sends a message stating he would surrender unless he is relieved. Both French sappers and English catapults manage to make significant breaches in the walls – but the assault is repulsed. Meanwhile, Richard I, still unable to walk due to illness, is carried on a regal stretcher near the front lines from where he picks off Muslim troops on the walls using his crossbow. July 12 – Siege of Acre: The Muslim garrison surrenders to Philip II, which includes an agreement to give up the 70 Muslim ships in the harbour without Saladin's consent, and by the time that he learned of this intention, the city has already capitulated. Conrad of Montferrat, who has negotiated the surrender, raises the banners of the Kingdom of Jerusalem, and of the Crusader leaders Philip II, Richard I, and Leopold V of Austria, on the city's walls and towers. The siege of Acre has taken nearly two years and has cost some 100,000 Christian casualties. July 31 – Philip II, accompanied by Conrad of Montferrat, departs to Tyre and returns to France. He leaves behind a French army (some 10,000 men) under the command of Hugh III, duke of Burgundy. Richard I is left in sole command of the Crusader forces in the Levant. Back in France, Philip schemes with Richard's brother, John of England, to dispossess Richard of his French lands while he is still away, but the intervention of John's mother, Queen Eleanor of Aquitaine, foils the plan. Meanwhile,