The Holy War, an allegory on the Christian life by John Bunyan, shows the impact of prayer on spiritual warfare.
“A petition was delivered to the King’s Son. He read it, and because it pleased him, he added some things and with his own hand carried it to the King. The petition made the King glad, but how much more, when it was seconded by His Son.*
Christ Jesus, who is at the right hand of God, also intercedes for us (from Romans 8:34).
*adapted from John Bunyan, The Holy War, p. 128-129.