Short answers, pulled from the story.
The German Army crossed into Austria on the 12th of March 1938 without firing a single shot. This event marked the end of Austrian independence and the beginning of its forced union with Nazi Germany.
Chancellor Kurt Schuschnigg served as the leader of Austria until he resigned under threat of invasion on the evening of the 11th of March 1938. He had previously met Hitler at Berchtesgaden where he agreed to appoint Arthur Seyss-Inquart as Minister of Public Security.
Germany sought rich raw materials including magnesium and iron ore mines at Erzberg along with gold reserves and foreign currency worth hundreds of millions. These assets were essential for Hermann Göring's steel programs and Hitler's military expansion goals.
Over 6,000 Jews were arrested overnight following the annexation and most were subsequently deported to Dachau concentration camp. By the end of 1941, more than 65,000 Viennese Jews had been deported to camps while fewer than 2,000 survived.
Mexico issued the loudest verbal protest when delegate Isidro Fabela denounced the action before the League of Nations. The Vatican also condemned Nazism in its newspaper L'Osservatore Romano and forbade Catholics from supporting the union.