The Navy brusquely fired the captain of the USS Enterprise on Tuesday, more than three years after he made lewd videos to boost morale for his crew, timing that put the military under pressure to explain why it acted only after the videos became public.

Senior military officials said they were trying to determine who among Navy leaders knew about the videos when they were shown repeatedly in 2006 and 2007 to thousands of crew members aboard the nuclear-powered aircraft carrier.