The Christians were greatly encouraged and launched a fierce assault on the walls of Acre. Catapults launched a relentless barrage of stones into the city, but Muslim resistance remained strong. Within Acre a catapult inflicted much damage to the Frankish machines. The Crusaders faced not simply the defenders of Acre, but Saladin's troop as well. When those in the city were under attack they would sound a drum to signal their co-religionists behind the Christians to launch an assault of their own. The Christians continued to exert maximum pressure on the walls, but still had to defend themselves from fierce attacks by Saladin's men. After days of siege the Christians lost momentum. Both Richard and Philip fell ill with scurvy, and had to take to their beds. Richard was determined not to let this deflect him, and he ordered himself carried to the walls, fired his crossbow at the city. Such resolution was inspirational to his troops. A fortification in the north-east of the city known as the "Accursed Tower" became the focus of Richard's efforts, it must have been a confusing and terrifyng fighting environment. Finally the Tower was brought down, but still the Muslims heroically resisted. By now, however, the walls of Acre had been pounded, pierced and shattered so many times that situation had become truly untenable. Negotiations began but Saladin could not agree to the crusaders' demands. Matters were to be taken out of his hands. He was devastated by this turn of events. At last the crusaders had achieved their goal... the defenders marched out. The European rulers then entered the devastated port. Richard's and Philip's banners were raised over the walls and towers.