The Senate on [March 6] rejected a ... bill to remove military commanders from decisions over the prosecution of sexual assault cases in the armed forces, delivering a defeat to advocacy groups that argued that wholesale changes are necessary to combat an epidemic of rapes and sexual assaults in the military. The measure, pushed by Senator Kirsten E. Gillibrand, Democrat of New York, received 55 votes - five short of the 60 votes needed. The vote came after a debate on the Senate floor filled with drama and accusations that Ms. Gillibrand and her allies were misguided. The debate pitted the Senate's 20 women against one another, and seemed bound to leave hard feelings, given that a solid majority of the Senate actually backed Ms. Gillibrand's proposal. Congress began scrutinizing the sexual assault problem in the military after a recent series of highly publicized cases, including one at the Naval Academy, and after the release of new data from the Pentagon on the issue. On Sept. 30, the end of the last fiscal year, about 1,600 sexual assault cases in the military were awaiting either action from commanders or the completion of criminal investigations. Critics of the military's handling of such cases say that the official numbers represent a tiny percentage of sexual assault cases, while Ms. Gillibrand said that only one in 10 sexual assaults were reported. She and her supporters argue that forcing victims to go to their commanders to report sexual assaults is similar to forcing a woman to tell her father that her brother has assaulted her.