I truly believe that having mandatory military service would be a great social benefit to our country.
Here are the reasons:
More manpower to provide for the defence of this nation, reducing obesity due to the high level of fitness attained, knowledge and respect of firearms gained during training, job security and skills that will serve the servicemember in future employment outside of the military, crime would likely decrease dramatically due to the sense of respect and honor that is instilled in recruits that they will take with them throughout the rest of their lives, it will create a society were congressmen/senators/presidents (having all had military experience) will make better judgements on whether or not the US should wage war since they would have to send their sons into battle