I found this fitting prayer in the General Prayers section of the Marine Corps Devotional Field Book (NAVMC 2765):
6. Prior to a Mission
O God, as we prepare to embark on this mission, we ask your presence to be made known to us anew! Give us wisdom in our decisions, common sense in our actions, discretion in our communications and openness in our attitude as we work together for the freedom of mankind. May your protective arm rest upon the shoulder of each Marine and Sailor in this operation and return us all safely home. Amen.
I also found this prayer for all involved in the war, at home or abroad:
9. For Those in Our Country's Service in Time of War
Almighty God, our heavenly Father, let thy protection be upon all those who are in the service of our country; guard them from all harm and danger of body and soul; sustain and comfort those at home, especially in their hours of loneliness, anxiety, and sorrow; prepare the dying for death and the living for thy service; give success to our arms on land and sea and in the air; and grant unto us and all nations a speedy, just and lasting peace. Amen.
These prayers say it all.
Dear Lord, hear our prayers.