When my youngest son joined the US Army, I had similar fears. When he was a baby, I had wondered if he might be autistic or something. He had some odd behaviors from the start. After having raised him and knowing what I know about Asperger's, I'd guess he also carries a few of the genes but he does all right, Like your son, he's never been one to pick fights. He also didn't have a lot of friends.
I had my reservations but it was his choice. He made the cut, which isn't easy these days, and off he went. I chose to support him any way I could, with my fingers crossed behind my back. I sent him twice-weekly letters during boot-camp because I remember my brother sharing with me how difficult it is emotionally. My mommy letters were just that. Coddling and encouraging with news from home. I kept my fears to myself.
He made it through boot camp with flying colors; one of the top 10 marksman out of over 80 troops. He's been to Afghanistan for one tour; he's home, recently married, and training for an anywhere-in-the-World, first-response team. (Just great...)
He's been the butt of jokes and some of the guys still make fun of his ways, and he doesn't always get it, but at the wedding I got the feeling that any one of those guys would go to the mat for him. They tell me he is very capable in combat and big enough to carry 3 men, for which 3 of them are very grateful.
My son has grown in ways I didn't expect. The Army really rounded him out nicely. His Dad ran out on us when he was just 6, so in a lot of ways, the Army did what his father refused and showed him how to be a man. I am supremely proud of the man he's become.
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Life isn't about waiting for the storm to pass; it's about learning to dance in the rain.