I think it's great that you want to do this dongyan, but something you need to consider is if it's something you want to do for the next 8 years. Your local recruiter can let you know for certain, but when I was of age many years ago, you joined up for 8 years. Most of the specialties only had a 2 year commitment, and the rest of the eight years could be either spent in a reserve like status, or active in the Army. Some specialties required 4 year commitments, and the other 4 years can be spent as you the same way - either active or reserve. I think the Navy is a minimum 4 year commitment out of the 8 years. I don't know about the Air Force. It could have changed by now, so make sure you check with your recruiting office.