It was the perfect afternoon to be on his yacht. Mansoor Ijaz, a global hedge fund manager with a home-office view of the French Riviera, says he planned to sail the Mediterranean on that sunny day in early May — but then his BlackBerry beeped.

“Are you in London?” the incoming message read. “I am here for just 36 hours. Can we meet . . . ?”

Thus began a weird diplomatic intrigue that led last week to the downfall of Husain Haqqani, Pakistan’s suave ambassador to Washington, and is still making waves in Islamabad. Ijaz, 50, a Pakistani American who grew up in rural Virginia, is at the center of the squall, a place the self-described “citizen diplomat” has landed before.

Rather than sailing, Ijaz says, he immediately phoned Haqqani, who’d sent the message, and spent the next several hours working back-channel Washington contacts at the ambassador’s request. He and Haqqani, who have known each other for years, exchanged messages using what Ijaz says were coded phrases — including “the three stooges” and “a sledgehammer with a golden handle.”

Why the secret-squirrel stuff? Because, by Ijaz’s account, Haqqani and Pakistani President Asif Ali Zardari were trying to prevent a coup by the country’s generals in the days after U.S. Navy SEALs killed Osama bin Laden. This involved getting a single-page, unsigned memo — seeking U.S. help to neuter Pakistan’s army and spy service — to the Pentagon.

Mansoor Ijaz and President Bill Clinton at a DSCC Fundraiser in 1996. (White House Photo/WHITE HOUSE PHOTO)

Ijaz is the bluff character behind the scandal dubbed “Memogate” by the Pakistani media. His version of events is vehemently disputed by Haqqani, whose role in the affair is now the subject of inquiries by Pakistan’s Parliament and Supreme Court. On Thursday, the court barred Haqqani from leaving Pakistan while it conducts a three-week investigation.

The matter would not have morphed into another “gate” had Ijaz not penned a Financial Times column in October calling for a clampdown on Pakistan’s jihadi-coddling spy service. Therein, he disclosed the existence of the memo and said it was delivered on the instructions of a “senior Pakistani diplomat.” Though the op-ed did not specifically name Haqqani, the connection was fairly obvious to insiders.

Critics call Ijaz an attention-craving Walter Mitty type, prone to exaggerating his importance in this and other murky international negotiations he has undertaken since the mid-1990s. But he calls himself a force for good, working to expose corrupt regimes, fight terrorism and uplift the oppressed, particularly in Muslim countries.

“I am driven by a sense of injustice,” he declares. “I believe I can change the world. . . . I fundamentally believe that my words, my actions, my interventions [in foreign affairs] have changed the course of history.”

Maybe so, but the only thing certain in Memogate is that the once warm and breezy relationship between Haqqani and Ijaz, two like-minded advocates for democracy in Pakistan, has hit an iceberg.

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The use of private conduits such as Ijaz is not unusual: Such people can prove useful to governments in making unofficial overtures to other governments. The memo, addressed to Adm. Mike Mullen, then chairman of the Joint Chiefs of Staff, said Zardari was willing to install a “new national security team” that would root out terrorists, including other al-Qaeda members sheltered by the Pakistani military. The document reached Mullen by way of Ijaz’s friend James L. Jones, the retired Marine general and former national security adviser.

But the Pentagon didn’t find the memo credible, and Mullen has said he ignored it. Zardari has not commented on it. One U.S. official called it “ludicrous”; another “ham-handed.”

The raid that killed bin Laden on May 2 caused a furor there, and a period of government destabilization, but top U.S. officials express bafflement over the notion that an overthrow of the civilian government was in the offing. In fact, Pakistan’s generals were busy trying to quell a revolt from their own troops, who were furious at the brass for not even knowing about the raid: The Americans had blindsided and humiliated them.

Haqqani, 55, who served in Washington for three years, is, like Ijaz, known for writings that lambaste the Pakistani military establishment. The BlackBerry Messenger traffic and the memo, preserved and later released to the media by Ijaz, seemed to substantiate their collaboration, but both deny they wrote the document. (Haqqani has said the messages were taken out of context but hasn’t disputed their authenticity.)

Some here and in the Pakistani capital consider both men to be incurable wheeler-dealers.

“Both Haqqani and Mansoor are of a kind,” says Ayaz Amir, an opposition member of parliament and prominent commentator. “Very quick . . . but a bit too smart for their own good.”

For his part, Ijaz says he never would have gotten involved in the matter, but did because his “close friend” Haqqani asked him to.

Haqqani responded in an e-mail: “Mr. Ijaz’s claims and assertions have put me and my family at risk in Pakistan. . . . The least he can do is to show some dignity in not exaggerating and describing me as a friend when his actions are far from friendly.”

As a back-channel operative, Ijaz has “finished himself now — no one will ever trust him to do anything like this again,” says Tim Carney, a former U.S. ambassador to Sudan who worked with Ijaz in 1997 on a Sudanese counterterrorism offer to the United States. “He’s completely burnt. We need to hear from Mansoor what he was thinking.”

The persistently loquacious Ijaz was happy to talk. For hours. In several telephone conversations, he insisted that he never meant to harm Haqqani, and issued a profanity-laced narrative of the Memogate episode and other operations.

He has no qualms about being egotistical, abrasive and loud.

“I speak truth to power,” he says when asked about the impression he makes. “When people say I overstate the truth, [expletive] them. They can’t handle the truth.”

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An interview with Mansoor Ijaz doesn’t get far before he provides a recitation of his common-man credentials: Born in Florida, he grew up on a farm in the Blue Ridge highlands township of Floyd, milked cows, walked a mile to school and struggled to pay tuition while earning his physics degree at the University of Virginia, with the help of a weightlifting scholarship.

Berfore he died in 1992, his father, Manaddid Ijaz, a physics professor at Virginia Tech, made videos for his children. The video for Mansoor contained this message:

“My father said, ‘I wanted to fix [the] problems of Pakistan, but my life has been cut short. And the one problem with you is, God gave you a great brain but a [expletive] personality. You have to get into politics to teach you humility.’ ”

By then, Ijaz had gained his master’s degree in engineering at MIT, devised a complex mathematical model for financial trading, started his own New York-based firm, Crescent Investment Management, and became wealthy. He later gave generously to Democratic politicians and causes and earned the favor of Bill Clinton and his circle. He mingled with the political elite and befriended bigwigs such as former CIA director James Woolsey, who became a corporate adviser.

As a prolific op-ed writer, he has railed against Pakistani government corruption (specifically targeting Benazir Bhutto, the former prime minister assassinated in 2007) and touted his work to improve American perceptions of Muslims as well as U.S. relations with Islamic governments. He became known for his efforts in Sudan and for trying in 2000 to broker a ceasefire deal between India and Pakistan over the Kashmir conflict. Both “interventions,” as he calls them, earned him supporters and detractors.

Not long after the Sept. 11, 2001, attacks, Ijaz enlisted Woolsey for a mission: They would fly on a private plane into Afghanistan to negotiate the release of humanitarian workers being held by the Taliban. Ijaz says they were also trying, behind the scenes, to secure a meeting with Taliban leader Mohammad Omar to convince him to “come clean” and hand over bin Laden, his deputy Ayman al-Zawahiri and other al-Qaeda operatives.

Woolsey says he has forgotten many of the details, but “it’s entirely plausible that Mansoor thought we could get something else. . . . It is not impossible that grander objectives could have been achieved.” The mission was scrubbed, though, when the U.S. bombing commenced.

The former CIA chief says Ijaz “frequently tries to do things that are difficult but helpful to people.” And, laughing heartily, Woolsey adds, “He is not a boring guy.”

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In Pakistan, some describe Ijaz as an example of those expats who seek respect in their ancestral country by cultivating connections with the powerful. “He wanted to be counted as a player,” says Mumtaz Ahmad, president of the Islamic International University and former Brookings Institution fellow who has followed Ijaz’s various exploits.

But because Ijaz isn’t from one of Pakistan’s known families, his American-won wealth and education do not count for much among the elite there.

“Influential people don’t migrate from Pakistan,” says Mohammad Malick, Islamabad editor of the News, a Pakistani newspaper. “Ninety-nine percent of people who have gone abroad are economic migrants, and you only become an economic migrant if you’re a nobody in Pakistan.”

No matter: Ijaz derives his identity from his U.S. citizenship, calls himself “the embodiment of the American dream” and says his wealth only matters in relation to the good he can do.

“God gave me so much in this world, but if all I left in the world was a jet on the runway, a yacht in the harbor, 10 homes around the world, and my wife’s 5,000 pairs of shoes, I will not have done my job,” he said.

After the Financial Times op-ed, the relationship between the ambassador and his businessman buddy became frosty, according to the BlackBerry messages proffered by Ijaz. “Basically you don’t get it,” Haqqani told Ijaz. “You have given hardliners in Pak Mil [the Pakistani military] reason to argue there was an effort to get US to conspire against Pak Mil.”

Ijaz responded: “I wrote one article.”

Haqqani: “Let this die down. We are in the right. We will still make things happen.”

When Pakistan’s foreign office issued a flat denial of the memo’s existence, and the press suggested Ijaz was a fantasist, he went into overdrive to prove the diplomat’s involvement.

“Attacks on my person will not be tolerated,” Ijaz wrote in November. “Stop telling lies about me and I might just [stop] telling the truth about you.”

Haqqani made another appeal: “If you were to listen to my advice, you would let this blow over.”

But the political storm, by then, was too fierce to weather. “When I look at this in hindsight,” Ijaz says, “I wish I had not answered the [BlackBerry] that day.”

Yachting might have been more pleasant.

Staff writers Karin Brulliard in Islamabad and Karen DeYoung in Washington contributed to this report.