Fasting is an integral component of training for the struggle against oppression.
The tyranny of desires and urges, the oppression of wants and appetites, of selfishness, are all subdued by fasting. The fast liberates one from the slavery of the soul to its various hungers, and this strengthens the soul and increases one’s courage.
Remember that when Rasulullah (Sallallahu ‘alayhi wa Sallam) mentioned the one day on, one day off fast of Nabi Dawud, he made a connection between Dawud’s fast and his bravery in battle.