Boril could never strengthen his rule which enabled Ivan Asen to muster an army and return to Bulgaria. He captured Tarnovo and blinded Boril in 1218. Initially, he supported the full communion of the Bulgarian Church with the Papacy and concluded alliances with the neighboring Catholic powers, Hungary and the Latin Empire of Constantinople. He tried to achieve the regency for the 11-year-old Latin Emperor, Baldwin II, after 1228, but the Latin aristocrats did not support Ivan Asen. He inflicted a crushing defeat on Theodore Komnenos Doukas of the Empire of Thessalonica, in the Battle of Klokotnitsa in 1230. Theodore's empire soon collapsed and Ivan Asen conquered large territories in Macedonia, Thessaly and Thrace.