What area did Hitler take over in western Czechoslovakia?

Hitler requested the return of the Sudetenland, which was heavily German speaking, at the Munich Conference.

The Czechs were against it not because they feared the loss of the territory - it was German speaking and not loyal to Czechoslovakia hence was a liability, but because it was mountainous and their fortifications were there. Once Germany controlled the Sudetenland it was a clear shot to Prague.