Question

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Answer 1

Well, before the A-bomb, nations had to use more conventional methods to wage war such as the use of ground forces, bombers, naval assets, etc.. to take strategic points and push ahead on the battlefield wherever it was. The Battle of Stalingrad, for example, lasted months.

With the A-bomb, both the Soviets and the United States can now wipe out entire cities with a single weapon. If the Nazis had the A-bomb, they could have just used it to annihilate Stalingrad instead of investing months in a losing battle to take it. It's that kind of "convenience" that has made the weapon so dangerous and which is one of the reasons we have had a Cold War instead of a hot one -- because now both sides have this weapon that can destroy so many lives in an instant. When both sides developed rockets powerful enough to send them around the world, it raised the stakes on the kind of destruction that could result.

Would you want to pick a fight with someone that had that up their sleeve? That's the use of deterrence. It's one of the reasons North Korea today is rattling its nuclear saber (though it's debatable just how many and how powerful their nukes really are).

Hope that nudges you in the right direction. Here are a few more links that might help out:

History.com - Cold War
http://www.history.com/topics/cold-war

Cold War - Lesson 4: Brinkmanship and Deterrence
http://www.youtube.com/watch?v=_yF536dG7R4