A Greek monk blamed Arab military success on Christian heresy, not Islam itself.

Evidence

Yet not once does he refer by name to Islam, Muslims, Muhammad, or the Koran. Monophysitism is a much larger preoccupation for Anastasius; this heresy, indeed, seems to be the root of the errors of the Arabs, and the Arab invasions themselves are punishments for the Monophysitism of Heraclius. — John V. Tolan, Saracens, 300

Categorization

• XREF: Connects to the broader Western tradition of explaining Islam as Christian heresy seen in later medieval polemics (Tolan’s own larger project).
• QUESTION: Worth verifying: was Monophysite attribution to the Arabs a widely shared view or idiosyncratic to Sinai monks?