 Complete the following phrase:  As a result of the growing discontent with his policy, Boril was overthrown in 1218 by Ivan Asen II, son of Ivan Asen I, who had lived in exile after Kaloyans death. After his coronation, Ivan Asen II arranged a wedding with Anna Maria, daughter of the Hungarian king Andrew II, and received the captured cities Belgrade and Braničevo as a dowry. He then signed an alliance with Theodore Komnenos, ruler of the most powerful Byzantine successor state, the Despotate of Epirus. With his northern border secured by the treaty, Theodore Komnenos conquered Salonica, greatly reducing the size of the Latin Empire. In 1225, Theodore proclaimed himself emperor. By 1228, the situation for the Latins became desperate; they entered into negotiations with Bulgaria, promising a marriage between the under-age emperor Baldwin II and Ivan Asen IIs daughter Helena. This marriage would have made the Bulgarian emperor a regent in Constantinople, but in the meantime the Latins offered the regency to the French nobleman John of Brienne. Concerned with the actions of the Bulgarians, while marching on Constantinople in 1230, Theodore Komnenos invaded Bulgaria with a huge army. Surprised, Ivan Asen II gathered a small force and moved to the south to engage them. Instead of a banner, he used the peace treaty with Theodores oath and seal stuck on his spear and won a major victory in the 