Ivan Asen II of Bulgaria
He was elected emperor in 1229 as the senior co-ruler (with Baldwin II) of the Latin Empire, and was crowned in Constantinople in 1231. John III Vatatzes, Emperor of Nicaea, and Ivan Asen II of Bulgaria occupied the last Latin territories in Thrace and Asia Minor, besieging Constantinople in early 1235. John directed the defence of his capital during the months-long siege, with the besiegers withdrawing only after Geoffrey II of Achaea and united fleets from Italian towns defeated their fleet in 1236. The following year, John died as a Franciscan friar.