Habsburg struggled in vain to keep the Nazis from annexing Austria before World War II, then campaigned against the Soviet empire in the decades after the war.
Otto von Habsburg: The obituary in the July 8 LATExtra section of Otto von Habsburg, oldest son of Austria-Hungary's last emperor, said that his father abdicated after World War I. Although his father did yield the throne, he did not formally abdicate. —
With the fall of the Berlin Wall in 1989, he used his seat in the European Parliament to lobby for expanding the European Union to include former Eastern Bloc nations.
He was a member of the European Parliament for the conservative Bavarian Christian Social Union in southern Germany and also served as president of the Pan-European League from 1979 to 1999. In that role, he was instrumental in helping organize the Pan-European Picnic peace demonstration in 1989 on the border of Austria and Hungary. The border was briefly opened in a symbolic gesture, which created the opportunity for 600 East Germans to flee communism months before the fall of the Berlin Wall.
It was the first time an Eastern European nation had opened its borders, and is widely seen as the start of the fall of communism.
The House of Habsburg rose to power in Europe at the end of the 13th century and at its height ruled much of the continent.
Born in 1912 in Reichenau, Austria, Otto von Habsburg became crown prince when his father, Charles I, was crowned emperor in 1916, during World War I.
But after Austria and Germany lost World War I, the Austria-Hungarian Empire was dismantled, Charles I had to abdicate, and Austria went on to become a republic.
In 1919, Charles and his family had to leave the country for what turned out to be permanent exile in several different countries, including Switzerland, Belgium and France.
After his father's death in 1922, the 9-year-old Otto officially took over as the head of the House of Habsburg.
Otto tried to negotiate his return to Austria in 1935 and again in 1938, when he even sought to become chancellor to fight the expected invasion by Hitler's troops, but could not gather enough support.
Instead, he found a channel through the U.S. Embassy in Paris to contact President Franklin D. Roosevelt and later claimed to have prevented Allied bombings of a number of Austrian cities by pleading with the U.S. military.
He was also credited with having helped about 15,000 Austrians, including many Jews, escape the Nazis. At the same time, as he told the Austrian paper Die Presse in 2007, he negotiated Austria's postwar fate with Roosevelt, Winston Churchill and Charles de Gaulle.
From early in World War II in 1940 to after the Allied invasion of France in 1944, Habsburg lived in Washington, D.C., before returning to Europe to live in France, and then in Poecking, Germany, after 1954.
Still, he was not allowed to return to Austria until 1966, five years after he officially renounced the crown. He later claimed to be baffled by the hostility and criticism he faced in his home country.
Despite his opposition to the Nazis, Habsburg was at times faulted at home for being too right-wing.
In 1961, Spanish dictator Francisco Franco offered to make him king of Spain after his own death. Habsburg declined, but later praised the fascist leader for helping refugees, calling him a "dictator of the South American type … not totalitarian like Hitler or Stalin."
Habsburg's wife, Regina, died last year. The couple had seven children. Their eldest son, Karl, now runs the family's affairs and has been the official head of the House of Habsburg since 2007.