Why did Chamberlain's policy of appeasement fail to prevent war?

Many politicians were in favour of appeasement but it was most associated with Neville Chamberlain. 

Arguments against appeasement- Many thought that it encouraged Hitler to become too aggressive.  It also allowed Germany to become too strong and put too much trust into Hitler's promises.  It also scared the USSR.

Arguments for appeasement- It was a way to prevent/delay war.  The economy was a far greater issue at the time.  If they did stand up to Hitler the USA wouldn't support them.  Hitler was standing up to communism which was a much bigger issue at the time.  Many colonies would not support a war with Germany and Britain weren't ready for war.  Many thought that the treaty of Versailles was too harsh.

Edward Benes the Czechoslovakian leader was horrified by the Anschluss.  He saw Czechoslovakia as next on Hitler's list for takeover.  The French were bound by a teaty to protect Czechoslavakia and the British felt obliged to help.  The leader of the Nazi party in Czechoslovakia stirred up trouble and Hitler stated that he would fight for Czechoslovakia if necessary.  Britain, France and the USSR all stated that they would support Czechoslovakia in a war with Germany.

Tension rose as Hitler began displaying his weaponry.  On the 15th September Chamberlain flew to see Hitler.  Hitler moderated his demands to only some parts of Czechoslovakia and only if won by a plebiscite.

On the 19th September Chamberlain and Deladier put this plan forward to Benes but at the next meeting 3 days later Hitler increases his demands.  He wanted all of the sudetenland and to justify this he said that the Germans in the area were mistreated.  

In the last meeeting with Mussolini's help on the 29th it was decided that Hotler would have all of the Sudetenland.  They did not consult the czech's in this decision.

Although the British people welcomed the Munich agreement they did not trust Hitler. In March 1939 they were proved right when he invaded the rest of Czechoslovakia.  Britain and France didnt do anything about this however, for Chamberlain this showed Hitler could not be trusted.  

It was now likely that Hitler's next target was Poland.  Britain and france told Hitler that if he invaded Poland they would declare war on Germany.  However, after years of appeasement Hitler didnt view this as a serious threat. 

Stalin and Hitler had contrasting beliefs and Hitler had claimed interest in claiming Russian territory.  Stalin tried to make agreements with Britain and France but these were not successful.  He had joined the League of Nations to gain security from Germany but he saw how the League did nothing but watch helplessly at the aggressor's actions.  In 1935 he signed a treaty with France that said France would help the USSR if Germans invaded but Stalin didn't have much hope they would honor this after seeing their actions in Czechoslovakia.  The Munich agreement worsened the situation as Stalin was not consulted in the decision.  Stalin concluded that they would be happy for him to expand east eventually reaching the USSR.

Stalin was still prepared to make an alliance with Britain and france and in March 1939 met but Chamberlain was still reluctant so negotiations continued.  However Ribbentrop the Nazi Foreign Minister also visited to draw up the Nazi-Soviet pact.  This stated they would not attack each other but privatley they agreed to split poland between them.  Stalin knew that Hitler wouldn't honor this pact however, this gave him time to prepare for war and he was not certain that Britain and france would be strong enough allies an=gainst Hitler.  He also had designs on Poland.

On 1st September 1939 Hitler invaded Poland from the west.    Hitler's next plan would be to invade the USSR but Hitler had a nasty surprise when Britain and France told Germany to pull out or they would go to war.  On the 2nd of September they declared war.  Hitler had taken too many risks and had started a war but not the war he had in mind. On the 17th of September Stalin invaded from the east.

Many think that the policy of appeasement had much to do with the origins of the Second World War as it encouraged Hitler to be aggressive and take big risks.