With David's most effective ally neutralized, Mehmed II marched to Trebizond. His fleet had landed there in early July, defeated David's army, and plundered the suburbs, besieging the city for more than a month. The Ottoman commander Mahmud Pasha Angelovic had opened negotiations with David even before his master's arrival, and David's "protovestiarios", George Amiroutzes, advised the emperor to surrender on terms. When Mehmed II arrived in August, he was displeased with the negotiations, but allowed them to proceed. David was now persuaded to surrender, keeping his family, household, and wealth, and was promised a profitable retirement in Thrace.