On 28–29 March 1938, Hitler held a series of secret meetings in Berlin with Konrad Henlein of the Sudeten German Party, the largest of the ethnic German parties of the Sudetenland. The men agreed that Henlein would demand increased autonomy for Sudeten Germans from the Czechoslovakian government, thus providing a pretext for German military action against Czechoslovakia.
In a speech in Wilhelmshaven for the launch of the battleship Tirpitz on 1 April, he threatened to denounce the Anglo-German Naval Agreement if the British continued to guarantee Polish independence, which he perceived as an "encirclement" policy.
His tasks for the Abwehr included collecting information on railways, military installations, and troop movements, as well as recruiting other spies within Czechoslovakia, in advance of a planned invasion of the country by Nazi Germany. He was arrested by the Czech government for espionage on 18 July 1938 and immediately imprisoned but was released as a political prisoner under the terms of the Munich Agreement, the instrument under which the Czech Sudetenland was annexed into Germany on 1 October.
Hitler began pressing German claims on the Sudetenland, an area of Czechoslovakia with a predominantly ethnic German population. Soon the United Kingdom and France followed the appeasement policy of British Prime Minister Neville Chamberlain and conceded this territory to Germany in the Munich Agreement, which was made against the wishes of the Czechoslovak government, in exchange for a promise of no further territorial demands.