Pope Martin I is known for his unwavering defence of orthodoxy, particularly in the face of the Monothelite heresy, which denied the full humanity of Jesus Christ. He convened the Lateran Council in 649 AD, which condemned the Monothelite heresy and affirmed the doctrine of the two wills of Christ – human and divine. Despite facing opposition and threats from political powers, Pope Martin I remained steadfast in upholding the teachings of the Church and defending the true faith.