As Christmas 2011 approached, U.S. Army medic Shawn Aiken was once again locked in desperate battle with a formidable foe: the U.S. Defense Department. Aiken ... was in his second month of physical and psychological reconstruction ... after two tours of combat duty. But the problem that loomed largest that holiday season was [that] Aiken had no money. The Defense Department was withholding big chunks of his pay ... and resisted Aiken's pleas for explanation and redress. The Defense Finance and Accounting Service, or DFAS ... is responsible for accurately paying America's 2.7 million active-duty and Reserve soldiers, sailors, airmen and Marines. It often fails at that task, a Reuters investigation finds. Aiken's case is hardly isolated. Pay errors in the military are widespread. Precise totals on the extent and cost of these mistakes are impossible to come by, and for the very reason the errors plague the military in the first place: the Defense Department's jury-rigged network of mostly incompatible computer systems for payroll and accounting, many of them decades old, long obsolete, and unable to communicate with each other. The department's authorized 2013 budget, after sequester, totals $565.8 billion - by far the largest chunk of the annual federal budget approved by Congress. Yet the Pentagon is literally unable to account for itself. A law in effect since 1992 requires annual audits of all federal agencies. The Pentagon alone has never complied. It annually reports to Congress that its books are in such disarray that an audit is impossible.