Otto denounced Nazism, stating: He strongly opposed the
Anschluss, and in 1938 requested Austrian Chancellor
Kurt Schuschnigg to resist
Nazi Germany. He supported international intervention According to Gerald Warner, "Austrian Jews were among the strongest supporters of a Habsburg restoration, since they believed the dynasty would give the nation sufficient resolve to stand up to the Third Reich". Following the German annexation of Austria, Otto was sentenced to death by the Nazi regime;
Rudolf Hess ordered that Otto was to be executed immediately if caught. As ordered by
Adolf Hitler, his personal property and that of the House of Habsburg were confiscated. It was not returned after the war. The so-called "
Habsburg Law", which had previously been repealed, was reintroduced by the Nazis. Otto's supporters, the leaders of the Austrian legitimist movement, were arrested by the Nazis and largely executed (
Stefan Zweig's novella
The Royal Game is based on these events). Otto's cousins
Max, Duke of Hohenberg, and
Prince Ernst of Hohenberg were arrested in
Vienna by the
Gestapo and sent to
Dachau concentration camp where they remained throughout Nazi rule. Otto was involved in helping around 15,000 Austrians, including thousands of Austrian Jews, flee the country at the beginning of the Second World War. After the
German invasion of France in 1940, the family left the French capital and fled to Portugal. On 12 June the Portuguese ruler
António Salazar issued instructions to the Portuguese consulates in France to provide
Infanta Maria Antónia of Portugal with Portuguese passports which would allow visas for her daughter Empress Zita and grandson Otto without violating Portuguese neutrality. The family resided in
Cascais during their exodus. When the German authorities pressed Salazar for Otto's extradition from Portugal, Salazar offered to protect Otto, but asked him as a friend to leave the country. Otto left, and lived from 1940 to 1944 in
Washington, D.C. In 1941, Hitler personally revoked the citizenship of Otto, his mother and his siblings, and the imperial-royal family found themselves
stateless. Otto was listed on the Nazi
Sonderfahndungsliste G.B. ("Special Search List Great Britain"), and was the unofficial head of numerous resistance groups in Central Europe. These groups hated Nazi ideology and saw the resurgence of a Danube confederation as the only way for small states to exist between Germany and Russia. They championed the centuries-old Habsburg principle of "live and let live" among ethnic groups, peoples, minorities, religions, cultures and languages. These imperial resistance groups became embroiled in ferocious partisan warfare against Hitler, who profoundly hated the Habsburg family tradition. Many of these imperial resistance fighters (according to current estimates 4000–4500) were sent directly to concentration camps without trial, and over 800 were executed by the Nazis. Among them was
Karl Burian, who was planning to blow up the
Gestapo headquarters in Vienna, or Dr.
Heinrich Maier, who passed on plans and production facilities for
V-2 rockets,
Tiger tanks and
Messerschmitt airplanes to the Allies. In contrast to many other German resistance groups, the Maier group was informed very early about the mass murder of Jews through its contacts with the Semperit factory near Auschwitz. During his wartime exile in the United States, Otto and his younger brothers were in direct contact with President
Franklin D. Roosevelt and the federal government. His efforts to create an "Austrian Battalion" in the
United States Army were delayed and never implemented. However, he successfully convinced the U.S. to halt or limit the bombardment of Austrian cities, especially Vienna; ==After World War II==