He was one of the world’s most ruthless heads of state. He also was one of the most outlandish. Rarely has the leader of such a small nation played such a large role on the international stage. But Moammar finally lost his invincibility as he fell to the superior fire power of NATO-backed Libyan rebel troops in his homeland, Sirte.

Gadhafi, who had weathered assassination attempts, US air strikes, and years of international sanctions, died today in the desert town of Sirte where he was born, the rebel coalition claimed.

Before there was Osama Bin Laden, there was Moammar Gadhafi. For years he was Public Enemy No. 1 in the US, feared and loathed for bankrolling terrorism and revolution around the globe.

A Newsweek cover story in 1981 branded him “the most dangerous man in the world.” To President Ronald Reagan, he was “the mad dog of the Middle East.”

And that was before his regime’s most dastardly deed of all: the 1988 bombing of Pan Am Flight 103 over Lockerbie, Scotland, by Libyan agents who planted explosives in a suitcase. The crash killed 270 people, most of them Americans.

And then, Gadhafi undertook an astonishing reversal. He was one of the first Arab leaders to denounce the September 11 terrorist attacks. Two years later, Libya abandoned its weapons of mass destruction programs, assumed responsibility for the Pan Am bombing and agreed to pay $2.7 billion in restitution to the families of Lockerbie victims.

The US reciprocated, resuming diplomatic relations with Tripoli and lifting economic sanctions. But while Gadhafi’s political conduct changed, his eccentric behavior did not. Across his four decades in power, he flouted all the rules for how a head of state should act.

He surrounded himself with gun-toting female bodyguards, and for years he traveled with a voluptuous Ukrainian nurse. He brought along a Bedouin tent to sleep in when he traveled abroad, and once attended a summit in Belgrade with six camels and two horses in tow. Gadhafi wore flowing robes, favored oversized sunglasses and received Botox injections.

“Can I ask you something very directly, which may seem rude?” ABC News’ Barbara Walters asked Gadhafi in a 1989 interview in Tripoli. “In our country, we read that you are unstable, we read that you are mad. Why do you think this is? … Does it make you angry?”

“Of course it irritates me,” Gadhafi replied. “Nevertheless, I do believe that a majority of the people in the four corners of the globe do love me.”

Libya was one of the world’s poorest nations when Gadhafi was born in a Bedouin tent in 1942 to illiterate parents. Young Moammar showed promise, and so he became the first member of his family to attend secondary school.

He harbored outsized ambitions even as a teenager. Enamored of Gen. Gamal Abdel Nasser’s rise to power in neighboring Egypt, Gadhafi began conspiring with high school classmates to stage a similar revolution in Libya.

In September 1969, Gadhafi lead a small band of junior military officers in a bloodless coup, toppling Libya’s pro-Western ruler, King Idris. It was an audacious move since Gadhafi was a mere army lieutenant, just 27 years old.

Initially, Gadhafi enjoyed broad support. He took no formal title, calling himself the Supreme Guide or Brotherly Leader. He created a system of government called the “Jamahiriya,” or state of the masses, which called for Libya to be governed by local councils. But there would be no collective rule.

Moammar Gadhafi’s Flamboyant Dictatorship Is Over

He transformed Libya into a dictatorship, criminalizing dissent, creating a network of informers and executing opponents. He sent hit squads to hunt down dissidents  “stray dogs,” he called them — who fled to Europe and the US.

Most significantly, Gadhafi squeezed foreign oil companies to give his regime nearly 80 percent of the revenue from Libya’s vast oil fields, a model that would be duplicated by other oil-producing states. It provided Gadhafi with the resources to cause havoc around the world. Harboring a deep resentment of the West, Gadhafi financed revolutionary movements in Africa, Asia and Europe — from the I.R.A. in Northern Ireland to Islamic radicals in the Philippines. He supported Palestinian terrorism, including the Black September movement blamed in the killing of Israeli athletes at the 1972 Munich Olympics.

Gadhafi’s conduct put him on a collision course with the United States. Soon after taking office, President Reagan severed diplomatic relations with Libya and slapped an embargo on its oil. Gadhafi upped the ante when Libyan agents orchestrated the bombing of a West Berlin disco in 1986, killing two U.S. servicemen. American warplanes bombed Gadhafi’s compound in retaliation, nearly killing the dictator.

The bombing of Pan Am Flight 103 cemented Libya’s standing as a rogue state. The ensuing sanctions against him were so severe, Barbara Walters needed the State Department’s permission to visit Libya to interview Gadhafi.

Asked in that interview about Washington’s demand that he needed to “renounce international terrorism,” Gadhafi laughed. “This could be the response when someone is sponsoring terrorism, but when our official position is that we are against terrorism, such demand would be meaningless,” he said.

Gadhafi scoffed when Walters brandished a report accusing him of using surrogates to commit terrorism around the world. “What is the practical evidence, the concrete evidence?” he said. “These are all lies … only ink and paper.”

All of which made Gadhafi’s about-face after 9/11, his rejection of terrorism, even more striking. Reportedly, he shared his intelligence files on al Qaeda with the CIA., and allowed the US to use a Libyan site for the harsh interrogation of a terror suspect.

With the lifting of sanctions, US and international companies rushed into Libya to do business. World leaders like Italy’s Silvio Berlusconi paid visits.

Gadhafi and his country were pariahs no more.

Now rehabilitated, Gadhafi cast himself as a statesman, and in early 2009, he was elected to lead the African Union, a confederation of 53 nations.

But the makeover unraveled in August 2009 after Scotland freed the only person convicted in the Lockerbie bombing, a former Libyan agent named Abdel Basset Ali al-Megrahi. Although the release was described as a humanitarian gesture — Megrahi suffered from prostate cancer  it triggered outrage in the U.S. and Britain. The outcry mushroomed when Megrahi returned to a hero’s welcome in Tripoli orchestrated by Gadhafi’s regime. Once again, Gadhafi appeared to be up to his old tricks.

Gadhafi’s ability to outrage was on full display during a subsequent visit to the United Nations General Assembly in New York.

Gadhafi ‘King of Kings’ No More

Introduced as “leader of the revolution, the president of the African Union, the king of kings of Africa,” Gadhafi railed and raged for 90 minutes, instead of the allotted 15. He ripped up a copy of the U.N. charter, demanded investigations into the assassinations of President John F. Kennedy and Martin Luther King Jr., and compared the U.N. Security Council to al Qaeda.

But it was the Arab Spring that led to be Gadhafi’s downfall. In February 2011, the anti-government protests roiling the Arab world spread to Libya with a Day of Rage challenging his rule. More than 40 years of anger and resentment exploded in demonstrations across the country.

When the protests morphed into an uprising, Gadhafi responded with extreme force. As Gadhafi’s forces closed in on the rebel stronghold of Benghazi, the UN Security Council authorized the use of force to protect civilians. And on March 19, US and European forces intervened, launching missiles and dropping bombs to assist the rebels.

The tide turned. In August, Gadhafi fled Tripoli as rebel forces closed in. After 42 years, his reign was over. But the wily leader’s whereabouts remained a mystery for months as the remnants of his security forces fought off rebels closing in on his strongholds.

At the time of his death, Gadhafi, his son Seif al-Islam and his chief of intelligence were wanted by the International Criminal Court in The Hague on charges of crimes against humanity for the killing, wounding and imprisonment of civilians during the early stages of Libya’s uprising.