What acts of aggression did Germany make in 1938-39 that ultimately led to the start of World War 2 in Europe?

In 1938, Hitler ordered the German army into Austria. Later that same year, thousands of Jewish shops and hundreds of Synagogues are burned down. In 1939, Germany invades Czechoslovakia. On September 1, Germany attacks Poland. France and The UK declare war on Germany two days later, and the war in Europe begins.