Anschluss

The Anschluss was the occupation and annexation of Austria into Nazi Germany in 1938. Although Austria had never been part of the modern state of Germany, there was solid support in both countries for the union. While Austrian Chancellor Kurt Schussnigg had attempted to forestall the issue with a referendum in March, 1938, the German Nazi Party supported a coup by its Austrian counter-part. Days later, German troops marched into the country.

The Anschluss was one more step on the path to World War II, as Adolf Hitler continued German remilitarization and expansion into 1939. Austria ceased to exist as an independent nation until 1955.

The Anschluss plays a background role in many works of Harry Turtledove with a Point of Divergence after 1938, although it's never been directly depicted. It is most immediately germaine to the following:

Anschluss in The War That Came Early
The Anschluss was one of several events Adolf Hitler counted as "achievements" on the eve of the Munich Conference in September, 1938, which for him made the Allied capitulation on the Sudetenland issue so frustrating. Thus, when it was announced that Konrad Henlein had been assassinated, Hitler gleefully declared war on Czechoslovakia. .

The annexed Austria became Germany's launchpad into Czechoslovakia days later.