My grandfather was a forward observer. His job was to go in to the beach first, climb a tree, and call in directions for the artillery that would bombard the defenses at the Japanese landing beach. In front of the invading army, these binoculars were made to resolve the targets of the first artillery barrages to soften its arrival on the beachhead. Picture the opening scene of Saving Private Ryan; the planned invasion of Japan would have been an amphibious assault on the scale of D-Day.
Artillery spotters like my grandfather had just about the lowest life expectancy of any troops in ground combat. He very likely would have died up in that tree, calling artillery directions into his radio.
Thankfully, he never had to go in first, to face the 2.3 million defending Japanese. The US command at the time made the right decision: finish the war as quickly as possible, with the fewest deaths on both sides.