The Axis were motivated by expansionism

The Axis primary nations were Germany, Japan and Italy.  Allied principles were the United States, United Kingdom, and the Soviet Union.  Each of these entities had their own vision and mission.

The Axis were motivated by expansionism.  Germany because of the self perceived humiliation after World War One and the Treaty of Versailles. (Trueman).  Japan was seeking expansionism due to

limitations they felt were on their emperor on the Japanese Islands.  Italy was seeking their own expansionism due in large part also to the Treaty of Versailles that ended the First World War.
Germany was the largest and most powerful of the Axis nations.  The vision of the nation was mirrored in the vision of their leader – Adolf Hitler.  He envisioned a powerful and dominating power
to repeat the glory of the German Empire (1871-1918) and the Holy Roman Empire.  These are the first two empires or Reich.  His motivation to the people was not one of conquest – but one of regaining what was rightfully theirs before the Treaty of Versailles.
To accomplish this he blamed the one group of people in the nation who had prospered since the end of the First World War.  These were the Jewish people.  He was able to unify the people under a common goal (becoming a strong nation again) and against a common enemy (the Jewish people and all who sympathized with them).
The Allied nations were unified under the doctrine of protectionism and repatriation of conquered nations that would be sympathetic with the Allied cause at wars end.
The United States was initiallymotivated by isolationism – the policy of staying out of the war.  Their sympathies were with the nations that were being attacked  and conquered by the Axis powers.
The USA initially wanted to stay out of the war – it was only after they were attacked by the Imperial Navy of Japan did they take an active role in the war.
By unifying the peoples of all the Allied nations against possible invasions by the Axis powers, was the United States able to build the coalition needed to defeat the Axis.
Individual human rights and national rights were the banners of unification used by the Allied powers.  No individual nation was strong enough to defeat the Axis Powers.  Unified the Allied Nations proved to be an unsurmountable body that was able to ultimately defeat the Axis nations – one by one.
Bibliography
Trueman, C.  (2000).  History Learnings.  The Treaty of Versailles.  Retrieved February 8, 2009 from http://www.historylearningsite.co.uk/treaty_of_versailles.htm