Please answer a question about the following article about Ashkenazi Jews:

Of the estimated 8.8 million Jews living in Europe at the beginning of World War II, the majority of whom were Ashkenazi, about 6 million – more than two-thirds – were systematically murdered in the Holocaust. These included 3 million of 3.3 million Polish Jews (91%); 900,000 of 1.5 million in Ukraine (60%); and 50–90% of the Jews of other Slavic nations, Germany, Hungary, and the Baltic states, and over 25% of the Jews in France. Sephardi communities suffered similar depletions in a few countries, including Greece, the Netherlands and the former Yugoslavia. As the large majority of the victims were Ashkenazi Jews, their percentage dropped from nearly 92% of world Jewry in 1931 to nearly 80% of world Jewry today. The Holocaust also effectively put an end to the dynamic development of the Yiddish language in the previous decades, as the vast majority of the Jewish victims of the Holocaust, around 5 million, were Yiddish speakers. Many of the surviving Ashkenazi Jews emigrated to countries such as Israel, Canada, Argentina, Australia, and the United States after the war.

The vast majority of the Jewish victims of the Holocaust spoke which language?
Yiddish