To provoke new hostilities, the French deliberately broke the treaty in 1839 by occupying Constantine. Abd al Qadir took up the holy war again, destroyed the French settlements on the Mitidja Plain, and at one point advanced to the outskirts of Algiers itself. He struck where the French were weakest and retreated when they advanced against him in greater strength. The government moved from camp to camp with the amir and his army. Gradually, however, superior French resources and manpower and the defection of tribal chieftains took their toll. Reinforcements poured into Algeria after 1840 until Bugeaud had at his disposal 108,000 men, one-third of the French army. Bugeaud's strategy was to destroy Abd al Qadir's bases, then to starve the population by destroying its means of subsistence--crops, orchards, and herds. On several occasions, French troops burned or asphyxiated noncombatants hiding from the terror in caves. One by one, the amir's strongholds fell to the French, and many of his ablest commanders were killed or captured so that by 1843 the Muslim state had collapsed. Abd al Qadir took refuge with his ally, the sultan of Morocco, Abd ar Rahman II, and launched raids into Algeria. However, Abd al Qadir was obliged to surrender to the commander of Oran Province, General Louis de Lamoricière, at the end of 1847.
Abd al Qadir was promised safe conduct to Egypt or Palestine if his followers laid down their arms and kept the peace. He accepted these conditions, but the minister of war--who years earlier as general in Algeria had been badly defeated by Abd al Qadir--had him consigned to prison in France.
In December 1840, France sent Marshal Thomas R. Bugeaud (1784-1849) to Algeria to begin a concerted military campaign to conquer Abd el-Kader's Algerians. The French drove Abd el-Kader into Morocco in 1841, where he enlisted the moroccans as allies in his war against the French. Abd el-Kader used his rifle-armed cavalry effectively, conducting incessant raids against French troops and then retreating. Finally, however, the French army under Bugeaud attacked Abd el-Kader's 45,000-man army at the Isly River on August 14, 1844, and decisively defeated it. After the Battle of Isly, Abd el-Kader took refuge in Morocco again in 1846 and, with a small band, fought small skirmishes against the French. Having lost the support of the sultan of Morocco and with few men left, Abd el-Kader surrendered to French general Christophe Lamoriciere (1806-65) in 1847.