The casus belli for Spain were the unrelenting attacks of Riffian tribesmen on Spanish settlements in North Africa but also the increasing pressure of Queen Isabella on congress to attack; following unfruitful negotiations with Sultan Abd al-Rahman vis-à-vis the reparations (the latter, unable to control the cabilas, actually died in the midst of negotiations and was replaced by his son Muhammad IV), a declaration of war propelled by Leopoldo O'Donnell was unanimously passed by the Congress of Deputies on 22 October 1859.

The skirmishes continued until January 31, when a Moroccan offensive action was contained, and O'Donnell began the march towards Tetouan, with the support of the Catalan volunteers.

The pressure of the Spanish artillery destroyed the Moroccan ranks to the point that the remains of this army took refuge in Tetouan, which fell on February 6.

The Moroccan historian Ahmad ibn Khalid al-Nasiri described the looting during the bombardment: A tumult broke out in the town,... the hand of the mob stretched out to plunder, and even [normal] people took off the cloak of decency.... People of the Jabal, and the Arabs, and the riffraff began to pillage and steal; they broke down the doors of the houses and the shops.... keeping at it the whole night until the morningOn February 5 the Spanish entered the city, ending both the battle and the war.

The treaty was indirectly influenced by the queen of Spain which demands were harsh for the Moroccan side and contemplated the extension on perpetuity of the Spanish presence in Ceuta and Melilla, the end of tribal raids on those cities, the recognition by Morocco of Spanish sovereignty over the Chafarinas Islands, the retrocession of the territory of Santa Cruz de la Mar Pequeña (a territory of uncertain location by that time, ultimately Ifni) to Spain in order to establish a fishing post, the permission to missionaries for establishing a Christian church in Tétouan, and the Spanish administration over the later city until reparations of 20,000,000 duros were paid.