It doesn't matter what your military ambitions may be.
Its not going to happen if you have Hepatitis B.
Aside from keeping up with your meds, and generaly keeping healthy, it is a highly contagious disease, and its not if you should get wounded and bleed every where, but just living in close contact with others on a prolonged basis has it risks.
The World Health Organisation states its between 50 to 100 times more infectious than HIV.
Unlike the HIV virus, the Hep B virus can survive outside its host for a short period of time. So any body fluids left behind by a sufferer is a likely source of infection.
Do you really expect to be allowed to serve alongside others while carrying a virus that is so high a risk?
Forget what you may of heard of the Foreign Legion taking anyone just to make up numbers. You will face a barrage of medical tests before you get anywhere near starting basic training. They do not want anyone with such a high risk condition serving within their ranks. Sorry to be so brutal about it.
Heres a link to the World Health Organisation's site and their information on Hep. B. You should know all this already.
http://www.who.int/mediacentre/factsheets/fs204/en/