You're a good friend. If he's in the right place in his life to accept that he needs help, he will be grateful for you starting the process. If he just gets mad, he probably needs the support even more, because he is incapable of seeing the damage he is doing to himself and others. My best friend since middle school dropped out of school for a year because of his relationship with alcohol, encouraged and supported by his 'brothers' in the fraternity he was involved with.
We're going to talk it out with him first and see what's going on. Our concern is that this guy commissions into the Army with the same (or worsened) behavior and becomes a problem for his unit. Junior officers always complain about having to pick up Private X from jail at 2AM and having to deal with PVT x, y, and z's DWIs-- thinking about it being the other way around when his subordinates see him like this... it's just not tolerable.