Letter LXXVIII is Leo’s first direct letter to Marcian following the November 450 exchange (Marcian’s Letter LXXVI, Pulcheria’s Letter LXXVII). Dated April 13, 451, it belongs to the pre-Chalcedon coordination period: the council that Marcian had proposed and Leo had accepted in principle was now being organized, and Leo’s legates — Abundius, Asterius, and others — were carrying the substantive correspondence while brief acknowledgment notes traveled through whatever messengers were available. The choice of Anatolius’s clerics as the bearers of this note is a quiet confirmation that the Roman-Constantinopolitan relationship has been normalized: Anatolius has subscribed to the Tome, Leo has accepted him as a brother bishop, and their respective clerics can now serve as ordinary couriers.

The letter is too short to carry much theological weight, but its opening phrase is worth noting: Marcian’s letters “pertain to the fulfillment of all prosperity.” This is Leo’s way of saying that a right-thinking emperor is not merely a political convenience but a sign of God’s providential ordering of human affairs. The emperor who defends the Catholic faith is the one God chose for the task — “as the matter itself shows” — and his reward will come from the one whose religion he defends. The contrast with Theodosius is implicit throughout: Theodosius had frustrated Leo’s every appeal; Marcian had immediately acted. The reward Leo promises is not diplomatic but theological: the one for whose religion Marcian is “so piously solicitous” will be his repayer in all things.