Henry Kissinger, who conducted U.S. diplomacy for two presidents during a war in Vietnam, tensions with the Soviet Union and upheaval in the Middle East, brings an incisive mind and a prickly personality to the new task assigned him by President Bush.
Kissinger, secretary of state to presidents Nixon and Ford, is one of the best known diplomats of the 20th century and one who stirred passions on all sides. He won the Nobel Peace Prize, but critics saw his actions in Southeast Asia as tantamount to war crimes and accused him of supporting Latin American dictators.
Now Bush has asked Kissinger to lead an independent investigation of the Sept. 11, 2001, attacks, hoping to answer many of the lingering mysteries about that day, including the possibility that the tragedy could have been averted if intelligence agencies had been more alert.
Kissinger, 79, pledged Wednesday to "go where the facts lead us. We are under no restrictions and we will accept no restrictions.''
Winston Lord, a former ambassador to China who is close to Kissinger, described Bush's choice as outstanding.
"He is a man of great stature, experience and prestige that cuts across party lines,'' Lord says. "He also has the trust of various players in the administration and that is important.''
In recent years, Kissinger has been looking after his lucrative global consulting business and making speeches to business leaders and other groups.
He speaks with the accent of his native Germany in a grave tone often mimicked by comedians. A recent television commercial for New York City tourism shows him sliding clumsily into home plate at Yankee Stadium wearing his trademark dark suit.
Kissinger won the Nobel Peace Prize in 1973 with North Vietnam's Le Duc Tho for the peace agreement they reached that year.
He made history when he traveled secretly to China in 1971, ending more than 20 years of estrangement between the United States and the communist giant. The trip opened the way for eventual normalization of relations with China.
Kissinger was also known for his efforts to achieve detente with the Soviet Union. The idea was to strengthen trade and economic ties with Moscow, giving the Soviets a stake in stable relations and perhaps taming Moscow's expansionist ambitions. The policy had mixed results.
He made a determined peacemaking effort in the Middle East, flying between Israel and Arab capitals in what become known as shuttle diplomacy.
Kissinger also was a steadying presence to many allies during the Watergate scandal that led to Nixon's resignation.
Still, his harshest critics have called him a war criminal for the role he played in Vietnam and Cambodia, and activists in Britain have persisted in efforts to bring him to court. Massive bombing campaigns were carried out in the region during his first four years in office.
He is resisting a request by Spain for questioning about his alleged knowledge of a plot by Latin American dictators to eliminate dissidents in the 1970s.
Kissinger said in a speech in London in April that mistakes "quite possibly'' were made in administrations in which he served but questioned whether it was appropriate now to revisit them, especially in court.
During his eight years in office, Kissinger was known as a demanding boss, often railing at subordinates. After Ford's loss to Jimmy Carter in the 1976 presidential election, Kissinger quipped that his own staff was relieved.
He was a little known Harvard academic when he became Nixon's national security adviser in 1969. He quickly became the dominant policymaking force, often keeping the State Department in the dark.
For example, Secretary of State William P. Rogers was not informed until the 11th hour of Nixon's plan to send troops into Cambodia in April 1970 to block North Vietnamese infiltration into South Vietnam.
Early during his service to Nixon, Kissinger became known as a ladies' man, sometimes dating starlets much younger than he was. "Power is a great aphrodisiac,'' he said.
Divorced at the time, he later married Nancy Maginnes, a former aide to the late New York Gov. Nelson Rockefeller, who brought Kissinger to Nixon's attention.
Besides serving as secretary of state, Kissinger also was national security adviser for Nixon and Ford. He held the two jobs simultaneously between October 1973 and October 1975, the only person ever to do so.
Kissinger was born in the southern German city of Fuerth. His family came to the United States in 1938 to escape Nazi persecution of Jews. Kissinger served in the U.S. Army in World War II and became a U.S. citizen in 1943.