This is a popular question that's asked a lot and has a lot of good posts answering it and is still in debate so new answers will pop up so as always more can be said on the subject!

This answer by /u/t-o-k-u-m-e- that's from the faq is a is very detailed and comphresive: http://www.reddit.com/r/AskHistorians/comments/u6qqo/there_has_been_some_controversy_on_the_true/c4sthrz/

This answer is 6 years old that draws mainly from one source and I've seen other quality posts that use other sources. In the mean while this link to the askhistorians FAQ will sate any hunger for more information on the Pacific War