Chrysocheir then staged another deep raid into Anatolia, reaching Ancyra and ravaging southern Galatia. Basil reacted by sending his relative, the Domestic of the Schools Christopher, against them. The Paulicians managed to avoid a clash, and as the campaigning season drew to a close, they began retiring towards their own territory. They encamped at Agranai (modern Muşali Kalesı) in the theme of Charsianon, with the shadowing Byzantine army making their camp at nearby Siboron (Σίβορον, modern Karamağara) to the west. From there, the Paulicians marched northeast to the pass of Bathys Ryax or Bathyryax (Βαθυρύαξ, "Deep Stream", modern Kalınırmak pass west of Sivas in Turkey), a location of strategic importance, as indicated by the fact that it served as a fortified assembly point (aplekton) for Byzantine expeditions to the East. Christopher sent the strategoi of the themes of Armeniakon and Charsianon ahead with some four to five thousand men, to make contact with the Paulician army, shadow it as far as the pass, and report on its intentions, i.e. whether it intended to double back westwards to resume raiding Byzantine territory or whether it headed back to Tephrike, in which case they would have to rejoin the Domestic's forces. When the two generals with their men reached the pass, night had fallen, and the Paulicians, apparently unaware that they were being followed, had made camp in the valley of the pass. The Byzantines took up position in a wooded hill called Zogoloenos that overlooked the Paulician encampment, which further concealed them from their enemy. At this point, the sources record that a dispute broke out between the men of the two thematic corps as to who was the bravest; the two generals decided to take advantage of their troops' high morale and impetuousness to attack, despite their orders. A picked detachment of 600 men from both divisions launched a surprise attack at dawn, while the rest of the army remained behind and made loud clamour with trumpets and drums, so as to suggest the imminent arrival of the entire Byzantine field army under Christopher. The ruse worked perfectly: the Paulicians, taken by surprise, panicked and dispersed without offering any serious resistance. The Paulician rout was completed as they fell upon the main Byzantine army while fleeing. Their remnants were pursued by the victorious Byzantines up to a distance of 50 km. Chrysocheir himself managed to escape with a small detachment