Funny, but "Thou shalt not kill" could be interpreted to mean not killing ANYTHING, including NON-humans, yet it is understood by most everybody that only humans were meant by that (well, maybe some Christians DO interpret it to mean all living things, and are the type of vegetarians that eat only fruits and such that don't involve killing plants).
So obviously as it is written, it isn't all-inclusive. Therefore, if it is shown that the old Hebrew meant "to murder", this shouldn't be hard to swallow either.
As for giving blessings, soldiers are going out into a dangerous situation. They MUST go out, that is the orders of their government, and put themselves in danger of being killed. Therefore, since many of these soldiers are believers in one god or other, I suppose the blessing would serve to comfort them somewhat, just as a blessing before climbing a mountain, entering an auto race, etc., might. As for those who don't believe, I don't think they mind necessarily either given the circumstances and that they like everyone else are working hard not to sh*t their pants at the present moment. ANY kind words would be welcome to them, methinks.