[3][4][5] Commanded by Bertrand Clauzel, the French expeditionary force amounting to 8,040 men and 30 officers,[1] left Bône on November 9; on the 18th, it crossed the pass of Râs-el-Akba and was only two marches from Constantine.

During the night, rain, snow and hail fell with such abundance and continuity that the soldiers, in the bivouac, were exposed to all the rigors of a Russian winter.

The city was defended by nature itself: a ravine 60 m wide, immense depth, and at the bottom of which flows the Rhummel wadi, presents for escarp and counterscarp a sheer-cut rock, unassailable by mine as by the ball.

The Mansourah plateau was connected to the city by a very narrow bridge leading to a very strong double door, well defended by the musketry fires of the houses and gardens which surround it.

Ahmed Bey shut himself up in Constantine and entrusted its defense to his general (khalifa) Ali Ben Aïssa, who has recruited about 1,200 soldiers, all of whom were determined to defend the city from French colonialism.

This first day was very difficult; the entire garrison and a multitude of cavalry attacked the rear guard fiercely, including Commander Nicolas Changarnier, of the 2nd Light Infantry.