 John was crowned emperor in <unk> Sophia in autumn 1231 ; by then , his territory was limited to Constantinople and its vicinity . The <unk> urged him to wage war against John III Vatatzes , Emperor of Nicaea , who supported a rebellion against their rule in Crete . According to Philippe <unk> ' <unk> Chronicle , John could make " neither war nor peace " ; because he did not invade the Empire of Nicaea , most French knights who accompanied him to Constantinople returned home after his coronation . To strengthen the Latin Empire 's financial position , Geoffrey II of Achaea ( John 's most powerful vassal ) gave him an annual subsidy of 30 @,@ 000 <unk> after his coronation . 
