Why were the British people expecting war in September 1938?
If they were expecting war, it was not immediately between
Germany and themselves. Hitler at the time was making threats and
incursions against Czechoslovakia, but although Czechoslovakia was
'created' by the Allies (including Britain) after WW 1, a defense
treaty existed only between that country and France, not
Up to then, Hitler had only annexed territories that had been
part of Germany anyway until 1918, and the Austrians had themselves
asked the Allies for a Union with Germany as far back as 1919 but
had been refused. Czechoslovakia also had been partly made up of
territories taken away from Germany after 1918 - most prominently
the Sudetenland. And is was generally agreed at the time that
Hitler's further-reaching ambitions were all directed eastward, not
against France or Britain.
So at the time the British people never felt themselves
threatened. But many feared that finally Britain would be dragged
into some military involvement by a country or ally crying out for
its help. So apart from a few 'cynics' like Winston Churchill, the
public in Britain generally stood firmly behind prime minister
Chamberlain's policy of containing Hitler's further ambitions by
the Munich treaty.