The US and its allies fought a brutal battle for about 6 months over these islands.
The naval battles were stupendous. The land battles were about the most brutal seen by the US marines in modern times.
Strangely enough the campaign ran almost concurrently with the Stalingrad campaign.
I personnaly see both to be the turning points in both theatres.
Interesting snippets include initial Japanese night superiotiry in naval battles and the tragic deaths of all the Sullivan brothers.
More here:
http://www.history.navy.mil/photos/events/wwii-pac/guadlcnl/guadlcnl.htm