[citation needed] In 634, the emperor sent his brother Theodore to fighting the invading armies of Arabs in Ajnadayn where he was decisively defeated.
On his retreat, Theodore blamed his brother's incestuous marriage to their niece Martina for the defeat of the Byzantine empire and delved into an argument with him.
This partly due to financial setbacks and the Byzantine empire failing to provide salaries for the troops, Trithyrius found himself in another role.
There was no enthusiasm towards joining the army, however the presence of the imperial paymaster encouraged mercenary recruitment.
[citation needed] The Muslim conquest of Syria appeared a significant threat to the Byzantine empire and Heraclius thus ordered Trithyrius to lead an army to counter the attacks.