Israel Calls up reservist. Preparing for War?

I've talked about it before how Israel would not stand for Iran becoming Nuclear. Now that they are pressing hard to achieve nuclear status the Israeli's are preparing to strike. I would dare to speculate that it is just a matter of time before Israel takes out Iranian nuclear facilities. Recently elected Prime Minister Netanyahu isn't one to sit around and wait to be attacked he will strike first. 

Now my concern is how will the U.S. respond when they do attack. Will they take the cowardly road and denounce the attacks(Which is what I expect of Obama) or will they stand with their long time ally and support them. When I look and see how the U.S. wants the Israeli's to split their land and create two separate states I have a feeling our president will not stand with them. My major concern is that Iran is receiving weapons from Russia and are allied with them. Will Russia join the fight if Israel attacks. I think they would see this as an opportunity to remove the Israeli nation. Will then the U.S. respond and help Israel.. Scary to think about