What was island hopping?

The term
island hopping is typically used with reference to .  Therefore, I have moved your question to
that section and I will assume that you are asking about that war.

The island
hopping strategy was used by the United States in its war against Japan in the Pacific.  The US
knew that, to win the war, it would have to at least threaten to invade the Japanese home
islands.  The problem was that Japan controlled many small islands between Hawaii and Japan and
between Australia and Japan.  If the US had attacked every Japanese-held island, the war would
have taken a long time and casualties would have been much higher than they were.  Therefore,
the US generally used the island-hopping strategy.  That is, they chose not to attack a number
of islands, instead simply bypassing them and attacking islands closer to Japan.  For example,
the US never tried to invade the large Japanese naval base at Truk.  Instead, it hopped past
that group of islands and invaded Guam and Saipan in the Marianas instead.  It left the Japanese
on Truk to wither on the vine instead of expending the resources needed to invade that island
group.