For reasons that are unknown, Theodore did not renew his attack on Constantinople in 1226 or the years thereafter. Instead, he seems to have occupied himself with domestic affairs, as well as taking care to improve relations with Frederick II during the latter's stop-over at Corfu and Cephallonia to lead the Sixth Crusade in 1228. In 1229, he even sent a company of Greek troops to serve under Frederick in Italy. At the same time, Theodore presided over a rupture in relations with Venice, after his governor in Corfu sequestered the cargo of a shipwrecked Venetian ship. Theodore issued an edict on 19 August 1228 prohibiting Venetian merchants from practising commerce in his realm. In January of the same year, Robert of Courtenay died, leaving the throne of the Latin Empire to his eleven-year-old brother, Baldwin II. With a regency taking over the governance of the state, the Latin Empire stood further enfeebled. At this moment, John Asen offered an alliance. Baldwin II would marry his daughter Helena, while John Asen would take over the regency and lend his assistance at repelling Theodore's attacks. The Latin barons viewed the offer with mistrust, as it would offer John Asen every opportunity to take over Constantinople himself; instead, they strung out negotiations, and eventually chose the 80-year-old but energetic John of Brienne () as regent. Although the Bulgarian offer failed, it served to open a rift between Theodore and his nominal ally. In a move clearly directed against John Asen, in September 1228, Theodore agreed to a one-year truce with the Latin Empire's regent, Narjot of Toucy, with the border between the two empires running along a line from Ainos to Vrysis.