When on the battlefield and your thirsty, the water in your canteen is not doing your body any good. Drink the water that you have in your in your canteen and put it in your belly. There is no reason to tote the water around till the end of the battle drinks it now.
Let me clarify the point that I am trying to make. In my years in the Marine Corps and in Reenacting I have had to deal with a good number of heat cases. Many of the victims had a canteen with plenty of water on their body when they went down. A full canteen did not do them any good. However if they drank the water that had on them then the odds would have been better that they would not have as much of a problem as they did.
Mark Wadsworth
16 March 2007