These are 4 levels
(FYI these are all my opinion so don't go around spreading unprofessional word)
I believe Pearl Harbor happened because multiple sources say that Pearl Harbor was attacked because it was close. On top of that, I personally believe also that more land could help the Nazis complete their evil plans.
All primary accounts are different because each were experienced by different people.
The primary accounts helped me understand the event because it let me get a picture of what it would have looked like pre-attack and how it effected family's.
Some factors that could have changed the outcome of the event could be if Hawaii was not close to Japan. Another could be if USA did not think the planes were their own coming back to Pearl Harbor.