Long before the first bullet was fired in World War II, the US government made a deal with its military - serve 20 years and receive a pension worth half of your pay.
Since then, it has been an untouchable political promise. President Barack Obama has called it a "moral obligation".
But given the nation's debt, it may not be an obligation that the US can afford to keep.
Having studied the matter, a high-level Pentagon board is recommending changes to the system the will affect those currently in uniform.
Al Jazeera's Patty Culhane reports from Washington, DC.