Putting the use of the senses in italics, the words in bold!
Answer:
Dearest Martha,
I cannot wait to return home to see you and everyone else. I miss you dearly, and each day I await for the day I can go home. The war's been at a stalemate for a long while, and I am afraid I'll be out here for the rest of my life.
Life, out here, is torture- I've scratched my arm on the barbed wire, and when I touch it, it hurts; the sharp barb also ripped my uniform, and the chill of the winds blowing through the trenches at night is bitter. I wish for my uniform to be sewn soon so that I can be warm, and for my arm to get the attention it needs. It's not like I could sleep even if I was warm, as I hear the screams of soldiers and the firing of military artillery- I do not know which side they're coming from.
The memories of what I've seen out here will haunt me forever. For a short time, my friend Lewis was on the front lines in a rush into the no man's land, and was shot in the head. I've never seen anything like it. Lewis didn't deserve that fate, and it was so cruel. I smelled the smoke from the gun that shot him, and I will never forget it, or the last dry and bland meal we tasted together. I will miss him.
I hope things get better, and that I can go home soon.
Sincerely,
(your son's name)
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I hope this is good, and that it lands him a good grade! Good luck :)