Albertone returned in Eritrea in 1895, when the tensions upon diverging interpretations of the Treaty of Wuchale between Italy and Ethiopia escalated into the First Italo-Ethiopian War. When the fighting started the Italian forces were divided into two operational Corps, one in Adigrat and the other in Mek'ele: the latter, almost entirely composed by ascari under general Arimondi, won the victory at Coatit, the opening engagement of the war. The Italian then invaded Tigray, while Menelik II was slowly gathering his forces in Addis Abeba. By November, when the negus finally started marching towards Italian positions, the occupation was complete, and a line of outposts and pickets was established on the borders. Realizing Menelik forces greatly outnumbered those units, Baratieri ordered a preemptive retreat. His conflictual relationship with Arimondi, however, led to the massacre of Toselli's column at the Amba Alagi and the loss of the isolated Fort of Mek'ele ("Macallè" in Italian sources) after a two-weeks siege.