On 9/11, they divided their effort in order to hit the Pentagon. They also apparently wanted the Capitol, but the Flight 93 passengers defeated their mission. If they'd tasked Flight 93 on New York not Washington, they might have succeeded. Short flight time from Boston might have deprived the passengers of time/info necessary to realize what was really going on.
Fort Hood, Chattanooga .... targeted on military personnel.
Ergo, expect more strikes on U.S. military, until/unless the jihadis get hold of nuclear weapons, then they'll go after densely-packed city centers.
I see mostly soft targets (like they did in France and elsewhere), but that’s not to deny the body counts and newsworthiness of the military targets...
http://www.thereligionofpeace.com/pages/americanattacks.htm
Historically, insurgents go after soft targets to demonstrate to the people that the govt cannot protect them, and the get the people to turn against the govt when they become heavy handed with the populace.
One hopes our own govt leaves Americans free to protect themselves.