The first several months of franklin delano roosevelt's presidency are often referred to as
a. a sweep of congress.
b. the great depression.
c. the "great days".
d. the "hundred days".

In my opinion, I'd say it was suprise, and timing. They attacked when most sailors were having their morning lunch, or were sleeping. So to conclude, the biggest advantage the Japanese had when attacking petal harbor would be their surprise attack and timing.