Otto von Habsburg saw the crumbling of the empire his family had ruled for centuries and emerged from its ashes as a champion of a united and democratic Europe.
The oldest son of Austria-Hungary's last emperor fought Nazism and Soviet communism during his long decades of exile from his homeland, and was lionized by leaders across the continent as "a great European."
Habsburg died Monday at age 98 in his villa in Poecking in southern Germany, where he had lived since the 1950s, with his seven children nearby, his spokeswoman Eva Demmerle told The Associated Press.
Habsburg used his influence in a vain struggle to keep the Nazis from annexing Austria before World War II, then campaigned for the opening of the Iron Curtain in the decades after the war.
With the fall of the Berlin Wall, he used his seat in European Parliament to lobby for expanding the European Union to include former Eastern bloc nations.
"My father was a towering personality," Habsburg's oldest son Karl Habsburg-Lothringen told the Austria Press Agency. "With him we lose a great European who has influenced everything we do today beyond measure."
Born in 1912 in Austria, Habsburg witnessed the family's decline after the empire was dismantled and Austria became a republic following World War I. He became head of the family at his father's death in 1922 and continued to claim the throne until the 1960s.
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.
European Commission President Jose Manuel Barroso mourned the passing of "a great European ... who gave an important impetus to the European project throughout his rich life".
"He made a central contribution to the opening of the Iron Curtain and the peaceful reunification of our continent that had been divided for too long," Barroso said in a statement. "I will particularly remember his strong stance against all forms of totalitarianism and on Europe's fundamental values."
Hungarian lawmakers held a minute of silence in parliament honoring Habsburg's memory, where he was remembered for his support through speeches given around the world of Hungary's failed 1956 revolution against Soviet occupation and for his backing of the country's efforts to join the European Union.
"His life and fate carried with it the history of the 20th century," parliamentary speaker Laszlo Kover said. After the fall of communism, "he personally did much to strengthen the process of our European integration."
Many in Hungary also respected Habsburg because of his ability to speak the famously difficult native language.
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 nine-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.
"Otto von Habsburg was one of the great personalities of modern European history," said Karl Hafen, head of the German chapter of the International Society for Human Rights.
"Habsburg was a great defender of freedom rights, a defender of minorities and ethnic groups and an influential statesman. His resistance to the Nazis, like his commitment to reconciliation and the unification of Europe influenced and inspired people."
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 rightwing.
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."
More recently he was criticized for remarks in 2008 in which he insisted Austrians were the victims of Hitler _ who was Austrian born _ rather than accomplices.
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.
Habsburg will be buried July 16 in the Emperor Tomb in Vienna, below the Austrian capital's Capuchin Church.
Before then, his body will be held in the St. Ulrich church in Poecking for three days for people to pay their respects.
Requiems are also planned for Poecking, Munich, Mariazell, Vienna and Budapest, Demmerle said.
Otto Almacht, an aide to Habsburg's son Georg, told the AP that Otto von Habsburg's heart would be buried in the Benedictine Abbey in Pannonhalma, central Hungary.
Gabriele Steinhauser in Brussels and Pablo Gorondi in Budapest contributed to this report.