Who told you that you have to do this? There are Christians in the military and I've never once heard anyone say they were required to cuss.

You will be tempted to cuss to fit in. But don't compromise. Of course God forgives but that doesn't mean you should disobey Him. Put Him first in all things. He will provide a way for you. Trust me, they aren't going to court martial you because you won't cuss. Remember the story of Daniel's friends, Shadrach, Meshach and Abednego who refused to worship the statue of the King. They refused to compromise and God honored them.

Read the story here
http://www.biblegateway.com/passage/?book_id=34&chapter=3&version=31