 Britain and France essentially acquiesced to Germany's rearmament ( )  Remilitarization of the Rhineland (1936)  And the annexation of Austria (March 1938).  All of the things above go against the Treaty of Versailles, so why do they let him do this?

 Appeasement in a political context, is a diplomatic policy of making political or material concessions to a (potential) enemy power (or powers) in order to avoid a threatened conflict.  Appeasement was used by European democracies in the 1930s who wished to avoid war with the dictatorships of Germany and Italy, bearing in mind the horrors of World War I.

 Hitler goes to Stalin and negotiates the signing of the German-Soviet Pact on 23 August  This Pact was to secure the new eastern border with the Soviet Union, prevent the emergence of a two-front war.  This Pact stated that Poland was to be partitioned between the two powers, enabled Germany to attack Poland without the fear of Soviet intervention.

 One of Adolf Hitler's first major foreign policy initiatives after coming to power was to sign a nonaggression pact with Poland in January  This move was not popular with many Germans who supported Hitler but resented the fact that Poland had received the former German provinces of West Prussia, Poznan, and Upper Silesia under the Treaty of Versailles after World War I.

 However, Hitler sought the nonaggression pact in order to neutralize the possibility of a French-Polish military alliance against Germany before Germany had a chance to rearm.

 Britain knew that something funny was up with Hitler and they were afraid.  Hitler was walking into lands where Germany was not allowed and building an army. This went against the Treaty of Versailles.  So Britain, with France, makes a pact with Poland and tells them that if they are invaded, Britain will fight for them.

 Second, the Blitzkrieg attacks in northern and western Europe (Operation Weserübung and the Battle of France respectively) to neutralize opposition from the west.  This resulted in the conquest of Denmark, Norway, Luxembourg, Belgium, the Netherlands, and France, all of which were under German rule by the early summer of 1940.

 WE ARE AT WAR AGAIN! YIKES!!