The Anschluss.
They didn't invade Germany. That was where it all started. Hitler was appointed to head and took over from there and started taking over other countries to gain more influence and power. He was a dictator through and through.
Austria-Hungary
Yes, Austria was essentially absorbed into the Third Reich though.
Austria-Hungary declared war on Serbia at the start of World War I.
France
Austria. They had been allies in WW1, but the Treaty of Versailles forbade their union after World War I.
The Anschluss.
Austria-Hungary did not exist after the First World War. Hitler acquired Austria as part of his expansion in Europe quiet early on, it was legalised through a referendum in Austria which saw 99% of the country vote for a union with Germany, or at least that's what the official papers said at the time.
Austria Hungary did not become one nation after World War 1.
From 1938 till 1945 Austria was a part of Germany, as it was annexed in March, 1938.
There was no Austria-Hungary after WWI it was broken up after the first world war
The treaty of Versailles
It was a World War because a man killed the archduke of Austria-Hungary in Sebia. Austria-Hungary declared war on Serbia. Serbia had an alliance with Russia and then Russia joined the war. Russia was in the Triple Entante and pulled Britain and France into the war. Austria-Hungary had alliances with Germany and the Ottoman Empire. They also joined the war. That is why World War I was a world war.
The 1st country to declare war on Serbia was Austria-Hungary.
They didn't invade Germany. That was where it all started. Hitler was appointed to head and took over from there and started taking over other countries to gain more influence and power. He was a dictator through and through.
Austria 1939