I disagree with defining terrorism so broadly. An act (or the ability to execute an act) of violence targeted against a civilian population is necessary to be considered terrorism. The FBI has been attempting to widen the definition over the past ten years (successfully I might add) & has clearly focused on helping groups gain (very minimally) the capabilities of executing a terrorist act.
I am not sure if the Pentagon is considered a military building or a civilian building (I think there is a valid argument to make that it is a civilian building.) I do not believe that the attack on the USS Cole should be classified as an act of terrorism.
As far as acts that resemble terrorism during war, they can be classified as war crimes. Actions during war have their own categories of law, so I would disagree with using the fire bombing of Dresden or the bombing of Tokyo as examples.
"The Pentagon is the headquarters of the United States Department of Defense, located in Arlington County, Virginia. As a symbol of the U.S. military, "the Pentagon" is often used metonymically to refer to the Department of Defense rather than the building itself."
You can find soldiers at the Tomb of the Unknown Soldier, that doesn't make the tomb a military installation. The mere presence of military personnel does not make a facility a military installation. Since the Pentagon is where the civilian leadership of the military is located, the building is arguably a civilian facility.
I am aware that JCS meets in the Pentagon, what is the point you are attempting to make? The fact is no troops are trained, quartered, & mobilized for war in the Pentagon. The Pentagon is a civilian location. In the U.S. civilians run the military (in other words the chiefs answer to their bosses, the secretaries, who answer to their boss the SecDef.)
Tora Bora is where the Taliban trained, mobilized, & quarter troops (even if they were irregulars.) This is the distinction between a military facility & a civilian facility that happens to deal with military affairs.
Terrorism is opposition to the current political setup. It's not _just_ that; there are other requirements (terrorism is a subclass of opposition, if you will) but I was simplifying in the service of an epigram. (",)
Totalitarian regimes' innovation is making opposition to the current political setup terrorism.