Boundaries changed frequently in Eastern Europe over centuries with war and the onset of different empires. The Austro Hungarian empire ruled by the Habsburgs was one such empire that included a huge part of central and eastern Europe at one time including Northern Italy, what became Yugoslavia in the 20th century, what became Czechoslovakia in the 20th century, as well as Galicia and parts of Poland etc.
I have been researching a Jewish family that lived in my house from the1940s to the 1990s having come to the UK in 1939 and 1940. The father of the house Leopold Lipmann Dukes b 1880 and his parents and siblings were born in Hlohovec now in Slovakia but then Galgocz in Hungary, part of the Austro Hungarian empire. This is near Bratislava, now the capital of Slovakia but once the capital of Hungary (this was new information for me). He always thought of himself as Hungarian even though as a young man he went to live in Vienna, had Viennese long term residency (he lived there 1910-1939) and his children were born in Vienna. And even when he Naturalized British, he thought of himself as Hungarian, even though the British thought he was German.
His nephew Ladislav/Ladislaus/Laci b 1908 came to UK in 1940 via a circuitous escape route including being deported from Palestine, and joining the Free Czech Army in France and then in Britain. His nationality on his papers was given as Czechoslovak, as this had come into being at the end of WW1, and Hlohovec in Slovakia was part of Czechoslovakia for much of the 20th century. However, on his British papers his nationality was given as Hungarian, and he never naturalized. When he died in a London asylum in 1983, his (Viennese born) cousin put his nationality down as Hungarian and not Czech or Slovak. Jews of the Austro Hungarian empire were fiercely loyal to Hungary and many took part in the 1848 uprising - which started in the town Cegled (south of Budapest) where Leopold Lipmann's wife was born in 1892.
So Austrian as a nationality on records does not necessarily mean that much, and may need to be qualified.
Jill Whitehead, Surrey, UK