Class Discussion Lead #2: Why Did the Allies Win World War II?

The Allies' victory in World War II is attributed to the sacrifice, perseverance, determination, strength, and raw willingness shown by the allied countries and their citizens.  The United States, Great Britain, and the Soviet Union put aside all political and financial grievances, to fight as one united army against Adolf Hitler.  Japan, also hoping to expand its territories, invaded and attacked numerous eastern countries during the same time that Hitler's army was wreaking havoc in Europe; thankfully, the two mass powers never joined forces.  Though Pearl Harbor was attacked by the Japanese, the United States only put 15% of their army towards the Pacific battle, and 85% directed against Germany.  The US and its allies fought enemies with automobiles and in warplanes; they also united in providing food, gas, and ammunition to the soldiers.  The Eastern attacks and Western attacks were separate battles- but fought by a united front of the world's superpowers against the independent Japan and Germany.  The defeat of Hitler was the ultimate goal of the Allies, and truly the only thing that united the countries who found themselves working together.  Germany was defeated due to the united front shown by these three mass armies, though not without millions of deaths to remind us of the battle.

Questions:

1. How did the communist Soviet Union and the democratic countries (US, Britain) find themselves working as a "United Front"?
2. Do you think Japan and Germany would have defeated the Allies if they had worked together?