Why did the united states develop the island-hopping strategy?

A military tactic to bypass heavily fortified Japanese positions and instead concentrate the limited Allied resources on strategically important islands that were not well defended but would help them get closer to Japan. 

On april 20, 1814, the dethroned emperor left france for the isle of  elba, where he was exiled under the terms of the treaty of fontainebleau.napoleon  would be allowed to ruleelba, which had 12,000 inhabitants. perhaps cruelly, the treaty allowed him to retain the title "emperor."