根据下面内容，回答题： Staff Sgt， Nicholas Lanier has entered what he calls the 'vast unknown. '' A combat veteran and father to four daughters， he can't remain in the military because of a serious back injury earned in Iraq. But he can't yet accept a civilian job because he doesn't know when the military will discharge（使退伍） him. He has no clue how much the government will pay him in disability compensation related to his injury， so he can't make a future budget. He just waits. Thousands of troops are like Lanier: not fully fit to serve but in limbo （无着落） for about two years waiting to get discharged under a new system that was supposed to be more efficient than its predecessor. And the delays are not only affecting service members， but the military's readiness as well. New troops can't enlist until others are discharged. The government determines the pay and benefits given to wounded， sick or injured troops for their military service. Under the old system， a medical board would determine their level of military compensation and the service member would be discharged. Then the veteran essentially would have to go through the process again with the Veterans Affairs Department to determine benefits. Under the new system， which started in 2007 and will be completely rolled out at military bases nationwide by the end of September， the service member essentially goes through both disability evaluation systems at the same time before leaving the military. But the new， supposedly streamlined，system is still such a cumbersome process that it's leaving many service members in limbo， they say. Why can‘t Sgt. Lanier serve in the military anymore? 查看材料