It really depends on what you want,the marines would probably be pretty difficult because they have the longest boot camp and they are also the smallest branch so they have fewer advancement opportunities and the like. Thats about all I know about the different branches. Are you going to enlist or be an officer?
Because if you go to college straight out of high school it's not that hard to get a completely full scholarship to do rotc in college.(you do have to agree for some service time afterwards though.)If you want to be enlisted the recruiter in my area said if you did at least two years of jrotc you get double promotion as soon as you finish bootcamp in any branch you join. He also said they will give you up to 40k of money to go to college while you are in the military. I don't know everything but I hope this helps some...
Out of all the choices you should pick navy.......you also forgot to mention coast guard. They are just like the navy and they help the country very much. They are also a very tough military branch to get into.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.