Guillet's Eritrean ascaris suffered losses of about 800 in little more than two years. In March 1941 his forces found themselves stranded outside the Italian lines. Guillet began a private war against the Allies. Hiding his uniform near a farm owned by Italian colonists, he conducted guerrilla raids with his remaining askaris against Allied forces for almost eight months. He was one of the most famous Italian "guerrilla officers" in Eritrea and northern Ethiopia during the Italian guerrilla war, a failed attempt to prevent Italian East Africa from being dissolved.