gee lets see, put 100,000+ men on a tiny island usually only a few miles wide/long where one side is entrenched so deeply that they have tunnels throughout the whole island which means that soldiers need to dig the enemy out of every single hole one at a time.
Right, sounds like a pushover.
America conducted D-Day style landings dozens of times over in the pacific, and the fighting was much much worse.
Just on okinawa alone the japanese suffered 110,000 killed and the americans suffered 90,000 casualties.