The return of the precious metals to the West indicated a revival of trade and a change in the form of competition. Instead of the imagination, the economic faculty began to predominate, and energy chose money as its vent. Within a generation the miracle fell decisively in power, and the beginning of this most crucial of social revolutions is visible in the third crusade, the famous expedition led by Philip Augustus and Cœur de Lion. These two great soldiers probably learned the art of fortification at the siege of Acre, the most remarkable passage of arms of the Middle Ages. The siege is said to have cost one hundred thousand lives, and certainly called forth all the engineering skill of the time. Guy de Lusignan, having been liberated by Saladin soon after Hattin, wandered about the country, abandoned and forlorn, until at last he sat down before Acre, in 1189, with a force inferior to the garrison. There he was joined by the kings of France and England, who succeeded in capturing the city after a desperate defence of two years. An immense booty was taken, but the clergy complained that two secular princes had embezzled the heritage of God. On the other hand, the troops had not received the usual assistance from miracles; for though assaults were delivered almost daily, none were worked, and the Virgin herself only appeared once, and then so quietly as to arouse no enthusiasm. After the surrender Philip went home, while Richard remained in command. The whole country had been overrun, only a few strongholds like the Krak des Chevaliers and Tortosa held out; and Richard, far from following the example of the first crusaders, who marched straight for the relics at Jerusalem, turned his attention to re-establishing the centres of trade upon the coast.