As for who was forcing who to start WWII, I believe that it was the harsh conditions of the treaty of versailles that lead to germany's ambitious needs... I won't go into why i think japan wanted to enter the war and sided with the axis.. (its kinda obvious, look at japan from a geographic standpoint and you will know what I mean)..
As for dropping the A-bombs, I don't think it was necessary.
However, I DO think that it was a much better alternative than invading japan. Most likey in the end, much of japan's cities would have lied in ruin, there would be millions of casulaties on both sides (especially tons of civilan casualties), and much of japans culture and hearatige that is still there today would have been wiped out. But also, I think that the USA could have dropped the A-bombs, most notably little boy (the one dropped on hiroshima) in a less densley populated area. It would have got the same message acrosss, and wouldnt have killed so many people.
I think the USA had another resason for dropping the A-bombs as well, as the USA realised the upcoming problems they were going to have to face with the Soviet Union's communist ways after the war, and they needed a way to show off to the Soviet Union the destructive power of their new weapon, and unfortunatley Hiroshima and Nagasaki were the two unlucky hosts...
Also, does anyone know what the Roentgen count at ground zero in hiroshima is? like... does it still have a high radiation count (at least compared to places where neuclear explosions didnt occur)?
Also... if you want to visit an interesting website... go to
http://www.kiddofspeed.com/ , its a site with pictures taken from a girl who constantly goes inside the "Dead Zone" near chernobyl, and has some pretty crazy picutres (especially the Ghost town near the reactor)... if you want the direct link with picures of the ghost town (and skip all of the stuff outside of the town before), the go to
http://www.kiddofspeed.com/chapter11.html
VISIT THAT SITE. It will totally open up your eyes to the devastating consequences of nuclear radiation (no it doesnt have any pictures of dead bodies, or anything greusome, so you dont need to be worried. Some of the pictures are kinda scary though (of the ghost town

)