A Christian Science perspective.
As our son prepares for his upcoming deployment in Afghanistan, the future of US and NATO military forces in that country is one of concern in our household. Increased troop levels and the probability of a long-term presence in that country mean that individuals serving in the military may spend multiple tours in harm's way. Already our son has served twice in Iraq, and our son-in-law, currently in Iraq, has done a tour of duty in Afghanistan.
Clearly, prayers for our loved ones and for all troops are an important and continuing way to support them and bring them all home when their missions are accomplished.
That prayers make it possible to avoid bloodshed even during wartime is shown in an interesting story in the Bible, found in II Kings, chapter 6. During the time of the prophet Elisha, the nation of Israel was threatened by Syrian aggression, and Elisha's prayers alerted him to the location of the armies so that Israel's king could avoid an ambush.
The Syrian king, frustrated, sent off his army to surround the city of Dothan and capture Elisha. But when Elisha's servant brought him word that they were in danger, the prophet's sense of God's presence was so strong that even the servant could suddenly see "horses and chariots of fire around Elisha." Elisha was able to divert the invading army to another area, from which they finally returned to their home base. In this instance, there were neither casualties nor collateral damage. Both sides of the conflict were protected.