Yow! Here's the story. My quick research seems to confirm that the military does have this sort of policy, on the theory that the bonus is an advance payment for a full term of service and the soldier isn't entitled to keep it unless he completes the full term -- even when the failure to complete the term is a result of a combat wound.

I should note, since this is a legal blog, that the military may well have a right under the terms of the enlistment contract to take back the bonus. It just strikes me as a scuzzy thing to do. Thanks to Victor Steinbok for the pointer.