• byzantine history
• Frederick II
• Hohenstaufen
• John III
• Lascarids
• mediterranean history

This thesis examines the subject of the diplomatic relationship between Frederick II and John III - an 'unholy alliance' culminated with the betrothal of John III and Constance, a natural daughter of Frederick, in 1242. A number of topics, often disregarded by the fragmented historiography on the subject, are addressed: the influence of Hohenstaufen rulership on the Nicene ally, the role of the alliance in the Realpolitik of the two rulers, the importance of the relationship with John III in altering Frederick's Balkan politic, and the fate of the alliance under their heirs. Alongside these general considerations, some narrower, more scholarly observations will also be proposed, particularly around the vexata quaestio of dating John III second marriage.