in late summer of 1240, taking an illegitimate daughter of Frederick II, Holy Roman Emperor, Constanza, whose name was changed to Anna. She was around ten and Vatatzes started a scandalous affair with one of her Italian ladies-in-waiting, named Marchesina. She was granted the right to wear purple shoes and to harness her horse with purple trappings, like the Emperor's closest relatives. Youth First administrative tasks If Vatatzes followed the practice of his predecessors, Theodore was proclaimed co-ruler while still a child. In his history, Akropolites mentioned Theodore as a co-emperor when narrating events that occurred from 1235 to 1237 and in 1242. In his correspondence, Theodore referred to himself as "my imperial majesty" from around 1242. He was not crowned during his father's lifetime—a likely explanation for the denial of his co-emperorship by two later Byzantine historians, George Pachymeres and Nicephorus Gregoras. Theodore's authority was considerable: he granted estates and salaries and intervened in legal disputes. On Blemmydes' petition, he ordered Nikephoros, the metropolitan bishop of Ephesus, to return an allegedly unlawfully purchased piece of land to Blemmydes' monastery. During his father's absence, he presided over sessions of the privy council and proposed candidates to vacant Church offices. John III Vatatzes again laid siege to Constantinople in May 1241, but he quickly realized he could not capture the city. He started peace negotiations, and Theodore accompanied his father to the meetings with the Latin envoys. They signed a two-year truce on 24 June. John II Asen died in the same month and his death weakened Bulgaria. Vatatzes launched a military campaign against the Bulgarians' Epirote allies late in 1241. Before departing for the military campaign, he appointed Theodore his lieutenant in Asia Minor. Theodore, like his father and grandfather, held an itinerant court and visited most Anatolian towns and villages. At this time, a Mongol general, Baiju, invaded Nicaea's eastern neighbor, the Seljuk Sultanate of Rum, from the east and captured Erzurum. Theodore informed his father, who was besieging Thessalonica, but Vatatzes did not abandon the siege. His persistence was rewarded when the ruler of Thessalonica John Komnenos Doukas renounced the title of emperor in return for the Byzantine court title of despot from Vatatzes. The Mongols launched a new military campaign against the Seljuks and routed Sultan Kaykhusraw II at the Battle of Köse Dağ on 26 June 1243. After the Seljuks agreed to pay a yearly tribute