Assou Ou Basslam was an Aït Atta tribal chief who led the final organised Berber resistance to French colonial pacification in southern Morocco. A leader of the Aït Atta n Umalu confederation in the eastern Anti-Atlas and southern High Atlas, he commanded the defence of the Bou Gafer plateau on the southeastern flank of the Jebel Saghro in February and March 1933.
The Aït Atta force at Bou Gafer numbered some four to six thousand fighters with their families, defending an elevated and water-poor plateau against a French expeditionary corps of more than eighty thousand troops with artillery and aerial bombardment. The siege lasted approximately fifty days. Assou Ou Basslam negotiated terms of surrender that preserved the customary law of the Aït Atta, prohibited French settlement on tribal lands, and exempted the surrendering fighters from punitive sanction; the protected population descended from the plateau in late March under those guarantees.
The fall of Bou Gafer was the last formal episode of Moroccan armed resistance to the French protectorate. Assou Ou Basslam returned to his home territory at Tagounit in the Saghro and lived there in semi-retirement under colonial supervision until his death in 1960, four years after Moroccan independence.
His reputation in the Aït Atta sphere combines military memory of Bou Gafer with the political achievement of the surrender terms, which contemporaneous observers and subsequent ethnographers — particularly David Hart — regarded as remarkable preservation of customary autonomy under conditions of overwhelming military disadvantage. He is the subject of a substantial corpus of Aït Atta and broader Tachelhit oral poetry collected from the 1960s onwards.