April 20, AD 624

Byzantine–Sasanian War of 602–628

Heraclius begins his 624 eastern offensive against Persia

Heraclius left Constantinople on the Feast of the Annunciation, paused to celebrate Easter with his family, and only then turned toward Persia.

The dates that are secure

The contemporary Chronicon Paschale supplies the framework: Heraclius left Constantinople for the east on 25 March 624 with Empress Martina and his children, then celebrated Easter near Nicomedia on 15 April.

Theophanes dates the emperor’s taking the offensive against Persia to 20 April, after Heraclius had offered peace and threatened invasion if Khosrow II refused.

Modern editors read that 20 April “invasion” as the start of the march for Persia — not a documented border crossing or battle that day.

A date rescued from the wrong year

Theophanes places the campaign in an erroneous chronological entry. Modern scholars keep his day and month but move the episode into 624, using the Chronicon Paschale and the securely dated end of the war.

The Greek expression translated “invaded Persia” may mean only that Heraclius started his march for Persia.

The chronology is unusually difficult in any case: Theophanes wrote about two centuries later, assigned later events a year too early, and combined material from lost sources.

Khosrow’s first move was not a battle

In Theophanes’s narrative, news of the offensive caused Khosrow to recall Shahrbaraz from Roman territory and to send Shahin with additional forces against Heraclius.

The immediate route led through eastern Anatolia and Armenia toward Sasanian-controlled Caucasian territory; attacks on Dvin, Nakhchivan and Ganzak came later in the campaign.

“Sassanid Empire (now Iran)” also misleads: the empire included Iran, Iraq, Armenia and other territories.

Sources

Researched 24 Aug 2026 7 sources not yet audited Date disputed

How this was checked

Researched from the web into a fact sheet and rewritten from that sheet. This article has not yet had an independent model audit. How the pipeline works →

Date disputed. Sources disagree about when this happened.

What the sources leave uncertain

The exact date is reconstructed. Theophanes gives 20 April but places the campaign in an erroneous chronological entry; modern scholars move it to 624 using the contemporary Chronicon Paschale and the securely dated end of the war.
The Chronicon Paschale dates departure from Constantinople to 25 March and Easter near Nicomedia to 15 April but does not itself name 20 April as an invasion date.
The Greek expression translated “invaded Persia” may mean that Heraclius started his march for Persia. It does not prove he physically crossed into the borders of modern Iran on 20 April.
Heraclius’s campaign chronology is unusually difficult because Theophanes wrote about two centuries later, assigned later events a year too early and combined material from lost sources.