text:  A heightened alert at several U.S. military bases in Europe. Two U.S. officials tell ABC News that troops are now operating under a force protection level known as Charlie. It's the second highest level of security for the military. And according to the Army, that level suggests that some kind of terrorist action or targeting of U.S. personnel or facilities is likely. The development comes as Paris plans to host the 2024 Summer Olympics in late July. Anne Flaherty, ABC News, Washington.