We underestimated the method the Japanese intended to fight in a number of cases ... but we bombarded the hell out of what we thought was there.
My father was personally, directly involved as an officer with a flotilla of LCI's.
Ultimately the Japanese spent less time on immediate shore forticifcations and more time on inland fortifications where they could maximize their attrition of our forces once they landed. That happened over and over in the Pacific. Tarawa was one significant departure from this ... but in most others their after-the-beach plans were carried out to significant effect ... albeit in almost all cases they suffered much higher casuality rates than we did and neither method prevented the inevitable.
Taiwan, in a simialr fashion, has spent much more on inland fortifications in the mountains (2/3rds of the island is very mountainous). 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.
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?