He rarely speaks in public and closely guards his privacy. But there's a growing consensus in America that it's Dick Cheney who calls the shots at the White House, on everything from the war in Iraq to climate change policy. Ed Pilkington reports

It is a party trick well known to curious teenagers across America. Zoom down on Washington via Google Earth and you get an extraordinary eagle-eyed view of the world's greatest powerhouse. There's the White House and its West Wing. There's the spot where they put the national Christmas tree festooned with lights. Sweeping south-east across the Potomac you soar above the pentagon of the Pentagon; then back up a bit north and you can sit for hours counting the tiles on the roof of the Lincoln memorial. But there is one thing you can't do. If you scroll over the site of the vice-president's official residence, all you will see, mysteriously, is a blurry fuzz.

The 46th vice-president of the US, Dick Cheney, has a fondness for remaining invisible. It doesn't matter whether it's Google Earth or a bank of television cameras, he won't play ball. He rarely presents himself to the media, and when he does so he likes to keep it in the family.

Take the interview he gave last October to Scott Hennen, a rightwing talkshow host with North Dakota's WDAY radio. At the time Iraq was imploding and the Republican party was heading towards meltdown at the mid-term elections. So what does Hennen ask him?

"Mr Vice-President, I know you're fond of pheasant hunting in South Dakota, but there's some great bird hunting in North Dakota. Is this going to be the year you come up and do a little bird hunting in North Dakota?"

Cheney: "Well, I don't know ..."

Incisive stuff. Hennen did, though, almost by accident, extract a seminal soundbite from the vice-president. The discussion turned to terrorism and where to draw the line on the interrogation of suspects.

Hennen: "Would you agree a dunk in water is a no-brainer if it can save lives?"

Cheney: "It's a no-brainer for me."

That quote, so innocently obtained, dunked Cheney himself in deep water. The man who had for months vehemently rejected the title of "vice-president for torture" found himself agreeing on air that the use of waterboarding - the technique of holding a prisoner underwater to the point of drowning in order to break their will - was a "no-brainer".

It was a moment of rare candidness from the ultimately controlled and secretive politician. For once that infamous steely guard that seems to shield Cheney - with his unreadable face and equally inscrutable half-smile - appeared to have slipped. Obscurity has been Cheney's hallmark since he took office in January 2001, and that's the way he likes it. "Am I the evil genius in the corner that nobody ever sees come out of his hole?" he quipped in 2004. "It's a nice way to operate, actually."

But what started as a single, unguarded gaffe last October appears nine months on to be developing into a pattern. Increasingly, the focus is switching from President Bush to the man who stands in the shadows behind him. This month sees the publication of two books analysing the role of Cheney, one by Stephen Hayes of the neocon bible the Weekly Standard, the second a more critical work called Opportunist, by Robert Sam Anson.

Those volumes will land before the dust has settled over a classic piece of Washington Post journalism. Under the headline "The Angler" - a reference to Cheney's secret service code name - two Post journalists, Barton Gellman and Jo Becker, have dissected Cheney's approach to his job in forensic detail. Virtually a book in its own right - the series runs to 20,000 words - they reveal how Cheney has dictated policy in several crucial areas, including the war on terror, the economy and the environment.

In all these polarised accounts Cheney is universally presented as the most powerful vice- president in American history. He has taken an institution that John Adams, its first holder, described as "the most insignificant office that ever the invention of man contrived" and turned it into a seat of power. "He has expanded the power of the vice-president fiftyfold," says Bruce Fein, a lawyer who served in the Reagan administration and who worked with Cheney during the Iran-Contra hearings. "Previous VPs typically handed out blankets in disaster zones or attended funerals in Burkina Faso."

Not Cheney. So dominant has he been in a traditionally submissive role that some commentators are now wondering whether it is time to drop the "V" from his title. "Cheney is de facto president in all areas of policy, bar just a few aspects of the domestic agenda," Fein says. Cheney's biographer, John Nichols, the Washington correspondent of the left-leaning Nation magazine, goes as far as to argue that "this was not George W Bush's presidency. It was Dick Cheney's."

In hindsight, it was obvious the Cheney vice- presidency was never going to stick to convention from the day in July 2000 George Bush announced his running mate. After all, the man who recommended Cheney for the job was ... Cheney. When Bush was asked to explain why he had gone along with such auto-selection, he replied: "I picked him because he is without a doubt fully capable of being president of the United States."

The moment the two men entered the White House it was clear Cheney had no intention of whiling away the hours at state funerals. The Bush cabinet was formed in Cheney's image. Figures who were to become seminal - Donald Rumsfeld, Paul Wolfowitz, John Bolton, Scooter Libby - were all Cheney's people.

In policy terms, too, his stamp was instantly visible, not least over the environment. Both Cheney and Bush are fossil-fuel men to their bone marrow - Bush through his family's oil connections in Texas and Cheney through the five years he spent in the 1990s as CEO of Halliburton. But early on it became clear that Cheney was prepared to go even further than Bush in his devotion to the industry.

In the 2000 election campaign, Bush had made much of his intention to cut carbon dioxide emissions from coal-burning power plants as part of a new push towards cleaner skies. But in March 2001, just two months into the administration, he announced a sudden policy reversal: there would be no new regulations after all. Administration officials told the New York Times that "the views of Dick Cheney had been instrumental in the final decision".

Cheney's stranglehold over energy policy was made official when he was put in charge of a task force to review the country's energy needs. The consequences were immediately apparent to those, like Eric Schaeffer, working to improve environmental standards. For 12 years Schaeffer worked at the Environmental Protection Agency, acting as chief enforcer of federal anti-pollution regulations. He remembers what happened when EPA scientists produced a report on the impact of clean-air restrictions on business, the findings of which ran counter to Cheney's preconceived opinions. "A few weeks later the report disappeared from the library - it was just wiped out," Schaeffer recalls. After months of similar irregularities, Schaeffer resigned in March 2002. "Government is a bargaining process and I know there has to be compromise. But equally, there has to be some respect for the facts," he says.

Schaeffer's boss at the EPA, Christie Whitman, resigned the following year. She said she wanted to spend more time with her family, but the Washington Post series finally reveals the real reason. She quit because Cheney - whom she had counted at one time as a friend - had ruthlessly blocked her every attempt to raise anti-pollution standards. When she tried to press her case directly to Bush, the vice-president was always in the room. "You leave and the vice-president's still there," she told the Post.

As Whitman's comment suggests, Cheney's impact has been partly due to his unparalleled access to Bush. Over six years in office, observers have seen a distinctive relationship develop between them. The older man is a master at the warp and weft of government. He revels in detail in a way that Bush notoriously does not. Bush's bed-at-nine routine may be exaggerated, but he certainly isn't up and reading dispatches by 4.30am as his VP is. Such precision gives Cheney an edge in any policy debate. As James Mann, author of a collective biography of the Bush cabinet, Rise of the Vulcans, puts it, Cheney is "the accountant who takes over the film studio".

These qualities of open access to the president, hard work and attention to detail were all present from day one. So too was a fondness for secrecy. Bob Woodward, in his account of the build-up to the Iraq war, Plan of Attack, likens him to a "kind of Howard Hughes, the reclusive man behind the scenes who would not answer questions".

But it took the events of September 11 2001 to bring these elements to the fore. This was the moment for which Cheney had been preparing for many years. Since his days as White House chief-of-staff to Gerald Ford, living with the fallout of Nixon's destruction, Cheney had harboured ambitions to hit back at Congress and reinstate the untrammelled authority of the president.

The Washington Post series examines the most controversial aspects of the administration's response to 9/11 - Guantánamo, the global kidnappings known as "extraordinary renditions", torture, wire-tapping of Americans - and finds that in all these cases the road leads to the vice-president's door. Within hours of the attacks on New York and Washington, while Bush was still floundering around in Air Force One, Cheney had assembled a legal team within his own office and was actively planning how to roll back the restraints on the president's executive power that had been introduced in the wake of Vietnam and Watergate.

Central to the team was Cheney's legal adviser, David Addington. By September 18 Addington and a couple of trusted colleagues, including the current attorney general, Alberto Gonzales, had drawn up proposals for the use of military force. By September 25 they had drafted authorisation for the interception of communications to and from America without court permission - a form of surveillance banned in federal law since 1978. By November 6 they had scripted a memo that conceived a whole new legal system that would allow alleged terrorists to be held indefinitely without charge. If necessary, they would be tried through "military commission" - a concept that Cheney put to Bush and had him approve personally over dinner.

Addington's team operated largely in secret. When CNN announced the military commissions on November 13, Colin Powell, the secretary of state whose more measured approach was to bring him increasingly in conflict with the vice- president, was heard to exclaim: "What the hell just happened?" Condoleezza Rice, then national security adviser, had also been left in the dark.

The pattern repeated itself the following year when Addington and his team, operating out of Cheney's office, drew up legal advice that in effect tore up the Geneva convention. Under its terms, the president had the right to order any means of interrogation of a terror suspect - by now designated "enemy combatants" - no matter how cruel or inhumane. According to the Washington Post, further secret opinion approved as lawful a range of previously banned interrogation techniques, including that little "dunk in water". The first time Powell and Rice heard about the torture memo was two years after it had been written; they read about it in a newspaper.

And then there was Iraq. If 9/11 was Cheney's moment, the invasion of Iraq in March 2003 may come to be seen as his undoing. Apart from his old mentor Rumsfeld, Cheney did more than any other member of the administration to lay the path to Baghdad. He had set his eyes on toppling Saddam well before 9/11, and by the time he entered the White House had already framed in his mind a rationale of pre-emptive military action. According to the former treasury secretary, Paul O'Neill, another friend of Cheney's who the vice-president ousted from the administration, Cheney was actively engaging in debate about "the next war in Iraq and the shape of a post-Saddam country" barely 10 days after the Bush administration took office.

Bush, by contrast, had no such appetite or vision. Consider the polar views that were expressed by the two men during their televised debates during the 2000 election. In debate with Al Gore, Bush said: "I just don't think it's the role of the United States to walk into a country and say, 'We do it this way; so should you.' "

Cheney struck a very different tone when, in debate with Joe Lieberman, he was asked what he would do were Iraq found to be developing weapons of mass destruction: "We'd have to give very serious consideration to military action to stop that activity," he replied.

Through the build-up to war, the VP was the rabble-rouser-in-chief, uttering his now famous prediction of the Iraqi people: "They will welcome us as liberators."

Iraq seems to have gripped Cheney with a passion that struck close observers as highly uncharacteristic. Woodward writes that Powell saw Cheney undergo a transformation. It was as though he had a fever, an unhealthy fixation in nailing Saddam. Fein detected a similar sea-change in the man. "I've been amazed by his change of character," he says. "When we served together on the Iran-Contra committee, he was measured, restrained, unflappable. Now he seems totally otherwise."

In all of this it would be crude to suggest, as some have, that Cheney called the shots while Bush merely saluted and shuffled behind. In the final analysis the buck stops with Dubya. But to say that Bush made all the big decisions, having duly taken the advice of his VP, would also be to miss the nuance of their relationship. In many cases the advice that Cheney gave his president was so narrowly cast that there could only be one serious outcome.

In the case of Iraq, the consequences for the country, the surrounding region and America's reputation in the world are now plain to see. What is less clear are the consequences for Cheney's own fortunes. Certainly, in recent months he has suffered a string of setbacks that have undoubtedly weakened his standing within the administration. While Bush is in the doldrums, with historically low personal poll ratings, Cheney too has suffered deep blows to his credibility. He has lost in the most humiliating circumstances several of his closest people: Rumsfeld, Bolton, Wolfowitz and now Libby have all fallen in quick succession.

The supreme court has also been nipping at Cheney's heels, overturning several important aspects of his anti-terror laws. In Rasul v Bush, the court threw out the White House argument that Guantánamo was beyond the reach of the US courts.

But it would be foolhardy to write off this supreme political machine quite yet. Terminator-style, he has a way of crawling back after every blow. The international lawyer Michael Ratner, president of the Centre for Constitutional Rights, has seen the phenomenon close up. He has argued against the administration before the supreme court on several occasions, and a pattern has emerged.

"Each time there has been a decision against Cheney he has come right back and changed the rules," he says.

With 18 months to go, the administration has undoubtedly now entered its lame-duck phase. Yet there is time enough for it still to cause trouble. For the past year a tug-of-war has been going on within the cabinet, with Bush in the middle. Rice, together with Rumsfeld's replacement at the Pentagon, Robert Gates, has been pulling the president in the direction of negotiating with Tehran over what the US claims is its nuclear weapons programme. On the other side, arguing doggedly that diplomacy is not enough and that military solutions may be necessary, is yet again Cheney.

Until recently the rope was moving decidedly in the Rice/Gates direction. But as the Guardian recently reported, the balance of the debate has just begun to swing back in Cheney's favour, behind a military option. Unthinkable though that may seem in the light of Iraq, he still appears to believe in the efficacy of shock and awe. The question now is: does he have one last gasp left in him?

All these struggles have left those at the sharp end of his dealings profoundly gloomy about America's future. "Dick Cheney has changed the whole landscape of the country," Ratner says. "And no matter who takes over from him, I'm not convinced we will ever get back to where we were before him".