Leo the Deacon
In early 970, a Rus' army, with large contingents of Bulgarians, Pechenegs, and Magyars, crossed the Balkan Mountains and headed south. The Rus' stormed the city of Philippopolis (now Plovdiv), and, according to Leo the Deacon, impaled 20,000 of its surviving inhabitants. Skleros, with an army of 10,000–12,000 men, confronted the Rus' advance near Arcadiopolis (now Luleburgaz) in early spring 970. The Byzantine general, whose army was considerably outnumbered, used a feigned retreat to draw the Pecheneg contingent away from the main army into a prepared ambush. The main Rus' army panicked and fled, suffering heavy casualties at the hands of the pursuing Byzantines. The Rus' withdrew north of the Balkan mountain range, which gave Tzimiskes time to deal with internal unrest and to assemble his forces.