On 15 March 1939, German troops marched into Czechoslovakia. They took over Bohemia, and established a protectorate over Slovakia.
Hitler's invasion of Czechoslovakia was the end of appeasement for several reasons:
it proved that Hitler had been lying at Munich
it showed that Hitler was not just interested in a Greater Germany (the Czechs were not Germans)
17 March 1939: Chamberlain gave a speech saying that he could not trust Hitler not to invade other countries
31 March 1939: Chamberlain guaranteed to defend Poland if Germany invaded
The takeover of Czechoslovakia in March 1939, allowed Germany to strengthen.
the large Czech army was removed as a threat
Czech airfields that were in range of many German cities were lost
the Czech armaments industry, including the Skoda works were taken over by Germany after March 1939. The German army took over large numbers of Czech tanks
The German invasion of Czechoslovakia in March 1939 brought an end to Neville Chamberlain's appeasement policy. Chamberlain offered to help Poland if it was attacked by Germany, and the British public now faced full scale preparations for war.