John Piper, The Pleasures of God

“Prayer is the walkie talkie on the battlefield of the world. It calls on God for courage (Eph. 6:19). It calls in for troop deployment and target location (Acts 13: 1-3). It calls in for protection and air cover (Matt. 6:13; Luke 21:36). It calls in for fire power to blast open a way for the Word (Col. 4:3). It calls in for the miracle of healing for the wounded soldiers (James 5:16). It calls in for supplies for the forces (Matt. 6:11; Phil. 4:6). And it calls in for needed reinforcements (Matt. 9:38). This is the place of prayer – on the battlefield of the world. It is a wartime walkie talkie for spiritual warfare, not a domestic intercom to increase comforts of the saints. And one of the reasons it malfunctions in the hands of so many Christian soldiers is that they have gone AWOL.”

Between Heaven and Earth: Prayers and Reflections that Celebrate an Intimate God. Copyright 1997 by Ken Gire.