Key word bolded. I've been to Okinawa and Iwo Jima; you can see bunkers that we never knew were there until YEARS later. A friend of mine found one the hard way in 1986--he stepped onto dirt supported by rotting logs, and his weight plus the dirt's weight was too much. Got himself a busted leg for his trouble.
No doubt, Taiwan will be a tough nut to crack and hold. The very attempt by the Chinese, requires that we not be there to interfere as a given and that is the principle point IMHO.
The problem here is consequence management: WTF do the ChiComs do if they take their best shot...and miss?