About military bonuses and taxes?

I was in the Army from Apr 2004 to Mar 2008. I got a $20000 bonus joining the Navy Reserves in March 2009 for 6 years. After taxes I got $14000. When I do my taxes, will I get the $6000 back when filing jointly with my wife? If something happens will I have to pay back the bonus like if they don't need me or my rate is overfull or medical? If I been in for 3 years and than got medically or something would I have to pay back the whole or some? Just curious.