I've always been an admirer of Israel's military system. Both men and women serve 2-3 years compulsory service to the country in some manner. At first, everyone needed to know basic military training, and I'm sure that went a long way towards their country being so strong now. There's more about it
here.
I agree with AGDee that the military isn't for everyone, but there are so many other options available to provide service to your country.