to resume negotiations about a church union with Pope Alexander IV and sent envoys to Rome in April or May 1256. Divergent views on the procession of the Holy Spirit had always been an important cause of the schism between the Orthodox and Catholic Churches. Orthodox theologians maintained that the Holy Spirit proceeded from the Father alone, while Catholic theologians stated that the Holy Spirit proceeded from the Father "and the Son". Theodore commissioned Blemmydes to summarize the Orthodox position. Blemmydes adopted a conciliatory approach, concluding that a statement about the procession of the Holy Spirit from the Father through the Son was fully in conformity with the Bible and the Church Fathers' works. Theodore did not accept his tutor's view and insisted on the traditional Orthodox doctrine. Michael II of Bulgaria dispatched Cuman raiders to plunder Thrace early in 1256. Although Theodore had instructed Laskaris and Margarites to adopt a defensive strategy, they pursued the Cumans, but the invaders inflicted a heavy defeat on their troops. Theodore assembled a new army, partially mustered among the Anatolian peasantry, and crossed the Hellespont. He sent troops, including Cuman horsemen in his service, against the invaders and they routed the enemy forces in two battles in Thrace. He entered into peace negotiations with Michael II with the mediation of Rostislav Mikhailovich, Duke of Macsó. Michael II had recently married Rostislav's daughter and Rostislav's wife, Anna of Hungary, was Theodore's cousin. Rostislav came to Thrace to reach an agreement with Theodore. Akropolites drafted a treaty about the restoration of the prewar boundaries between Nicaea and Bulgaria. Rostislav accepted it and signed the peace treaty on Michael II's behalf on 29 June. The treaty prescribed that Michael II cede Tzepaina to the Nicaeans, but the Bulgarian garrison was not withdrawn immediately from the fortress. Theodore became convinced that Rostislav had deceived him and ordered the public whipping of Akropolites. His act proved imprudent, because the Bulgarians ceded the fortress in early September. Theodore sent George Mouzalon to Akropolites to seek a reconciliation. The peace treaty aroused much indignation in Bulgaria, enabling Michael II's cousin, Kaliman, to stage a plot and dethrone the Tzar. Kaliman seized the throne, but he never gained the support of the army. After he fell victim to a new plot, Rostislav Mikhailovich and Michael II's brother-in-law, Mitso, laid claim to the throne. Most boyars (noblemen) preferred a third candidate, one