General Clausel was appointed a second time to replace d'Erlon and led an attack against Mascara in December of that year, which Abd al-Qādir, with advance warning, had evacuated.

Abd al-Qādir continued to harry the French at Tlemcen and so additional troops, under Thomas Robert Bugeaud, a veteran of the Napoleonic Wars experienced in irregular warfare, were sent from Oran to secure control up to the Tafna River and to resupply the garrison.

Abd al-Qādir used the Treaty of Tafna to consolidate his power over tribes throughout the interior by establishing new cities far from French control.

Throughout 1840, he waged guerilla war against the French in the provinces of Algiers and Oran, which Valée's failures to deal with adequately led to his replacement in December 1840 by General Bugeaud.

Bugeaud instituted a strategy of scorched earth, combined with fast-moving cavalry columns like those used by Abd al-Qādir to take territory from him gradually.

[9] In the early 20th century, France faced numerous incidents, attacks and looting by uncontrolled armed groups in the newly occupied areas in the south of Oran.

[10] Under the command of General Hubert Lyautey, the French Army's mission was to protect the areas newly controlled in the west of Algeria, near the poorly-defined Moroccan boundaries.

[10] On 17 August 1903, the first battle of the South-Oranese campaign took place in Taghit in which French Foreign legionnaires were assailed by a contingent of more than 1,000 well-equipped Berbers.

[10] A few days after the Battle of Taghit, 148 legionnaires of the 22nd mounted company, from the 2e REI, commanded by Captain Vauchez and Lieutenant Selchauhansen, 20 Spahis and 2 Mokhaznis, forming part of escorting a supply convoy, were ambushed, on September 2, by 3,000 Moroccans tribesmen, at El-Moungar.

Returning from an investigation trip to Algeria, Tocqueville wrote that "we make war much more barbaric than the Arabs themselves [...] it is for their part that civilization is situated.

"[12] The scorched earth policy, decided by Governor General Bugeaud, had devastating effects on the socio-economic and food balances of the country: "we fire little gunshot, we burn all douars, all villages, all huts; the enemy flees across taking his flock.

"[12] According to Olivier Le Cour Grandmaison, the colonisation of Algeria led to the extermination of a third of the population from multiple causes (massacres, deportations, famines or epidemics) that were all interrelated.

A long shadow of genocidal hatred persisted, provoking a French author to protest in 1882 that in Algeria, "we hear it repeated every day that we must expel the native and if necessary destroy him."