Would capturing ther capital not destroy the enemy power structure? The plan I'd have thought would be to bypass non-capital cities, as Taw had mentioned, then capture the capital, then the other cities should surrender.
Good point, but please understand, by the time an invasion starts, the "enemy power structure" as you call it, assuming you mean the governing agency, has been long gone, as weve seen with countless other invasions, to name one, the Blitzkrieg of 1940, where Holland was invaded, the royal family split, the queen went with her husband to London, her daughter and granddaughter (which now is seated on the throne) went off to Canada. as in, they were gone, almost before the invasion started.
Mostly, Capitals have more of a status of civil control, then an actual status of strategical importance, as opposed to the old days, when all the generals, and the copuntry's leader and his strategical staff was seated in the capital city of said country, when fallen, the whole country would be disoriented, along the strategical principal of: "Strong as a wilderbeast might be, with the head severed, its as useless as a pair of wasted socks".
I mean, todays example (sorry to bring the US into this) would be the US, when the nation is under attack (Like 9/11, sorry again) a plan that has been practised to the points of utter boredom steps into place, the president is immediately flown off to a safehouse, his wife and (possible) kids, are also flown off, but usually in the opposite direction of that of the nations leader, the vice president and the chiefs of staff will be scattered around the country, under their respective departments, in a connection with the leader of said country, from where they will coordinate the defenses of the country, should one fall, another can always step in, and in case the president, or the presidents wife be captured, and held ransom, communications with either are terminated, and may it be the president, shame, but the next one (read: Vice president) can always take over, should his wifes location be uncovered, "sorry mr. president, find a new wife, and raise a family with her". cruelly said, I know, but it comes down to it.