Rupert Cornwell: The man who knows nearly everything

Another autumn, a different president and a different war – but a familiar ritual was playing out in Washington last week. A new Bob Woodward book is coming out. The choreography never changes – much speculation over shock revelations, advance copies quietly slipped to The New York Times and The Washington Post to whet interest further – and bingo, another mega-seller, this one entitled Obama's Wars, glides down the publishers' slipway into a hugely lucrative literary ocean.

At 67, Woodward has long evolved from junior Post reporter assigned to the Watergate scandal into a journalistic institution surely without parallel anywhere. He is the modern equivalent of a medieval court scribe, neither a propagandist nor partisan. He seems to have equal and virtually unlimited access to Democratic and Republican administrations alike – the key players under Bush the elder and Clinton, Bush the younger and Obama have all opened up to him.

His books (this is the 16th of them) follow a similar pattern. Woodward is non-judgemental. He offers scant analysis, no opinions and no attitude – except perhaps in State of Denial, his third book on George W Bush's wars, in which the author's anger, at the botched follow-up to the invasion and the debacle over Saddam's non-existent WMDs, is unmistakable. The anger, one suspects, was partly directed at himself for having got it wrong. The dysfunctional and incurious Bush Jnr who emerges from that book is light years removed from the crisp, decisive and idealistic leader who features in its two predecessors.

As a rule, though, Woodward keeps himself entirely out of the narrative. Instead we gain an unrivalled fly-on-the-wall account of meetings, memos and emails, of divisions and personal feuds, and the ferocious inter-agency intrigues that shape decision-making in Washington.

Bush's war was Iraq, Obama's is Afghanistan. In the new book we learn of this president's frustration with the Pentagon, at its failure to provide an exit strategy from Afghanistan, and how he dictated his own six- page document to define the military's mission and to prevent that mission from expanding. Then there are the usual juicy personal titbits. A former CIA director refers to the current director, Leon Panetta, as the "goombah" of the White House chief of staff, Rahm Emanuel (goombah, you may be interested to learn, apparently being a slang term for an Italian-American, derived from "cumpà", the Neapolitan dialect word for "compare" or godfather). Elsewhere, Vice-President Joe Biden refers to Richard Holbrooke, the special US envoy for Afghanistan and Pakistan, as "the most egotistical bastard I've ever met". To which veteran observers of the steam-rolling Holbrooke will, of course, wearily respond: "What else is new?" And in truth, the agonising and the infighting come as no great surprise.

Throughout last autumn, as the administration carried out its Afghan policy review, the papers were full of the disagreements between top advisers over the size of any troop surge, and the open dispute between the US ambassador in Kabul and the US commander in Afghanistan over whether there should be a surge – not to mention the subsequent indiscretions to Rolling Stone magazine that cost that commander, General Stanley McChrystal, his job.

Even so, I reckon that on the Richter scale of Woodward books, this one will rank fairly high. The war is unpopular and not going well, despite the surge of 30,000 troops announced by the President.

The staff rows throw into even sharper relief the contradictions in the Obama policy: a big force increase now, coupled with a promise to start pulling out those forces next July. Is the President's heart really in this seemingly unwinnable war, you will ask.

Probably wisely, the White House is not disputing any of the book's contents. To do so would merely prolong its political shelflife. Indeed, when confronted by the same question as its predecessors – what do we do about Woodward? – this administration seems have decided quickly to haul up the white flag: if he wants to speak to cabinet secretary X or top official Y, then let him.

Which brings us to the Woodward modus operandi. Make no mistake, he is a remarkable investigative reporter, perhaps the best in the business. He is charming, and has a way of making people open up to him. It helps, too, that his subjects know that others are talking to him. If official Y is going to trash me, our cabinet secretary X might reasonably reckon, then I'll talk to Woodward too, to get my trashing in first. In the end, Woodward gets the story, or a pretty reasonable approximation thereof.

Christopher Hitchens once dismissed him as a "stenographer to the stars", and undoubtedly Woodward has mutated from the young upstart who, along with Carl Bernstein, cracked Watergate, to the ultimate (and now extremely rich) insider. But the spirit of All the President's Men is not entirely dead. The story goes he had been unsuccessfully trying to interview a prominent general for his final book about George W Bush. After receiving no answer to repeated emails and phone calls, he turned up unannounced at the general's front door one evening. "Are you still doing this stuff?" the amazed general is said to have asked, before inviting Woodward in and telling all.

And so the ritual goes on. The advance print for Obama's Wars is already 630,000. Today's Sunday talk shows will be full of it, while The Washington Post will serialise lengthy chunks from tomorrow. Meanwhile the agonising over Afghanistan goes on, too. A further policy review is set for December – and doubtless Bob Woodward is already drawing up a synopsis for Obama's Wars Part Two.