Abstract: Act II of Le Cavalier seul evokes the Byzantium of the first Crusade. While it reflects a well-known anti-Byzantinism, it nonetheless conforms to historical truth by more or less faithfully reconstructing the pomp of the imperial court, the surprise of the Byzantines at the arrival of the crusaders, and the doctrinal (double procession of the Holy Spirit) and ecclesiological (opposing ideas on the government of the Church) disagreements that have separated, in principle since 1054, Eastern and Latin Christians.
