A lot of gangbangers in the military these days also. I've seen several documentary's about that over the years. Even US gang graffiti over in the middle east where our troops have been deployed. Not to say it's all gangbangers but I would be willing to bet quite a bit.
Thirty years ago we had one or two from east LA one step ahead of a judge. Most got straightened out or kicked out but even then you could see where things were headed. They had to be handled with kid gloves, couldn't say certain things, etc.
I honestly don't know how we possibly could field a fighting force today.