Therefore...

Therefore, the theory that Umar's conversion to Islam caused Muslims to abandon their caution and defensive posture, and to defy the infidels, is simply not coincident with facts. S. Margoliouth .....we have no record of any occasion on which Umar displayed remarkable courage, though many examples are at hand of his cruelty and bloodthirstiness; at the battle of Hunain he ran away, and on another occasion owed his life to the good nature of an enemy.

(Mohammed and the Rise of Islam, 1931) Professor Margoliouth has made a reference to the occasion when a good-natured enemy…