Its 328 pages were an intense study of the legacies of a war that had stretched the US military, riven world opinion and deeply divided American political life. It was entitled The American Military and the Lessons of Vietnam. In one passage, the young officer took on the idea that public opinion in the US could not abide a military quagmire. 'Vietnam was an extremely painful reminder that, when it comes to intervention, time and patience are not American virtues in abundant supply,' Petraeus wrote in 1987. Now Petraeus is delivering another survey of an unpopular, divisive war. Only this time his audience is not a college tutor: it is the whole world.

In less than two weeks, Petraeus will appear before the US Congress and deliver a report into the progress of the 'surge', the military strategy launched by President George W Bush that was designed to win the Iraq war. It has been billed as a 'make or break' moment that could either trigger the beginnings of an American withdrawal or build on the first signs of real military success. And it will be scoured anxiously in London, where the political debate about the timing of a withdrawal of the remaining British forces is gathering pace.

In America, both sides of the political divide are breathless in anticipation. The Democrats await any hint of criticism. The Republicans have prepared a PR barrage of 'good news' to try to turn public opinion back behind the war effort. White House officials hail Petraeus as a 'warrior scholar' who finally gets what is needed to win in Iraq. They see him as a man who can save the Bush presidency.

But the reality is far more complex. The brutal truth is that the Petraeus report is unlikely to change a thing when it comes to policy on the ground: the surge and the war will go on. Its true importance lies in how it will be used politically: by the White House, by leading Democrats such as Senator Hillary Clinton, by Republican presidential hopefuls such as Rudy Giuliani.

And not least by Petraeus himself. For the highly media-savvy general has political ambitions of his own. This is his moment to shine.

A story often told about General David Howell Petraeus concerns a brush with death at Kentucky's Fort Campbell in 1991. During a training exercise, a soldier tripped and accidentally fired his rifle. The bullet hit Petraeus in the chest. Yet he refused to leave the exercise, only relenting when a more senior general ordered him carried away on a stretcher. Even then - with the bullet missing his heart by inches - he managed to get himself discharged early from hospital after he did 50 push-ups in front of his doctor, just a few days after being shot.

The anecdote leaves little doubt that Petraeus is tough and driven. He was born in 1952 to Dutch American parents - his father, Sextus, was a seaman - and he grew up in the upstate New York town of Cornwall. It lies almost in the shadow of West Point, America's military academy, where Petraeus duly gained admission. He excelled at high school and then graduated in the top 5 per cent of the West Point class of 1974. He also married the superintendent's daughter. From there he carved out a successful career culminating in the rank of general.

A reputation as a 'Washington general' was wiped out by two tours of duty in Iraq. First he led his unit in the 2003 invasion of Iraq, and then won plaudits for pacifying the northern city of Mosul in 2004. Then he took charge of the retraining and rebuilding of Iraq's army, again winning praise for swiftly and decisively bringing on the scheme. He then co-authored the military's new manual of counter-insurgency before, at the start of 2007, being appointed to command US forces in Iraq.

'He's a straight talker and he's very highly thought of militarily,' said Professor Donald Goldstein, a military expert at the University of Pittsburgh. Petraeus fits a lot of energy and focus into his 5ft 9in frame. He is famed for his five-mile runs, carried out even on Baghdad's hottest days. One subordinate called him the 'most competitive man on earth'. But his macho army bluster is also tempered by a keen intellect. His Princeton PhD is no accident. He is flexible too: he knows the war in Iraq is rarely just about bombs and bullets. In Mosul, one of his most famous catchphrases on the subject of bringing peace to the city was 'money is ammunition'.

Yet he is not without critics. Some say he is overly fond of the media and has skilfully crafted an almost flawless public persona of the skilled tactician. Others say his focus is not just about the facts on the ground, but about his own advancement. 'He is a sycophant incarnate. He's a smart guy, but he's playing politics in this,' said Larry Johnson, a former CIA anti-terrorism official. They also point out that Petraeus's record in Iraq can be criticised. The peace he brought to Mosul proved shortlived, and there is now a criminal investigation into missing supplies and weapons that involves officials close to Petraeus. His time in Iraq has seen the emergence of death squads and heightened sectarianism. 'This has all happened on his watch,' said Johnson.

But what will his report say? First, some media spin needs to be cut through. Petraeus has been used as an impressive, patriotic figure on which to hang such an important study. That suits both the White House and Petraeus himself. But his tough persona masks a more nuanced approach from the administration.

In fact, the Petraeus report will be a mix of analyses from Petraeus and the US ambassador to Iraq, Ryan Crocker. Its exact wording will have heavy influence from White House officials. For those hoping that the report will contain a damning indictment of the war or prompt any meaningful troop reduction - or full withdrawal - there is almost certain to be deep disappointment. 'It is frankly delusional for anyone to think it is going to change policy,' said Charles Pena, a senior fellow at think-tank the Independent Institute. 'They [Petraeus and Crocker] have no choice but to try to implement administration policy.'

And that policy is showing some signs of success. The military surge of troop numbers pushed by Bush has had an impact. The report will probably point to success stories in former hotbeds of Sunni insurgency such as Ramadi, Tal Afar and Mosul, where the security situation has been brought under some degree of control. In these areas, strategic alliances with Sunni tribes have seen former insurgents working with the US against Islamic jihadists. 'There has been progress militarily. It is fair to say that,' said Professor Rick Stoll, a defence and warfare expert at Rice University.

A taste of what Petraeus's presentation might look like has already been given. On a recent trip by Democrat and Republican politicians to Iraq, he sat down, armed with charts and Powerpoint slides, to illustrate the advances made by the surge. An account of the meeting by Democrat Congresswoman Jan Schakowsky gives the lie to anyone expecting a military withdrawal from Iraq. She revealed to one newspaper that Petraeus told her America would be in Iraq in some way 'for nine to 10 years'.

While the surge has changed the nature of the conflict, it has not yet brought it much closer to an end. As the brutal Sunni insurgency has tailed off, it has been replaced by Shia violence. The report is likely to note that the war has now become a fight between Shia militant groups and the US military. By last July, according to US officials, Shia fighters accounted for 73 per cent of attacks on coalition forces. That has been matched by a total failure of the Iraqi political process and a collapse of relations between the majority Shia - represented by Prime Minister Nouri al-Maliki - and the US. The surge's aim was to 'buy time' for reconciliation between Iraq's warring sectarian factions, but instead the feuding blocs have grown more violently apart. 'No one wants to talk about reconciliation. No one wants to listen,' said one official recently returned from Iraq. 'The only reconciliation that is taking place is between the US military and some Sunni insurgents. That is not going to solve Iraq's problems in the long run.'

So that will be the twin messages of Petraeus and Crocker. The military aspect of the surge is starting to turn the tide. But the political opportunity it was designed to create is being wasted by the Iraqis. If that sounds familiar, that is because it is the official White House stance on Iraq. 'He is going to say that, from a military standpoint, it is going well, but, from a political standpoint, it is difficult and the Iraqis have to stand up for themselves. That is what Bush says,' said Goldstein.

But if the contents of the report appear predictable, its impact is harder to ascertain. One thing is clear: it is unlikely to precipitate any rush significantly to withdraw US forces. It will allow the White House to claim that its strategy is working and that to halt the surge - as most Democrats wish to do - would be to snatch victory away from their troops.

Most experts believe that the White House will keep US troop levels at the current force of about 160,000 until at least April. Then to maintain the surge the army would need to extend its current rotation period from 15 months to 18 months. That is seen as too much of a burden by many military leaders.

Therefore it is widely predicted that the US presence in Iraq could be down to pre-surge levels of 130,000 troops by September next year. That could be presented as the beginning of a withdrawal, but it is hardly the sort of conflict-ending momentum that many Democrats - and much of the American public - seem to want. However, there is little political pressure on Bush to change policy in Iraq. He does not face re-election and the Democrats have shown that they are unwilling to do the one thing that could end the war: cut off funding. Again, the Petraeus report will not provide them with motivation to harden their stance. 'The President has called the Democrats' bluff. They don't have the stomach for defunding, so there is no political pressure on the White House,' said Pena.

But that is not true for any of the presidential candidates. They are all feeling the heat. For the Democrats, the Petraeus report is likely to contain enough bad news for them to continue their largely symbolic push for a troop withdrawal, but it will also have the risk that they will look as if they are undermining the first signs of success on the ground. For Republicans, it poses the opposite problem. The top-tier candidates, such as Rudy Giuliani and Mitt Romney, have seen what happened to the campaign of John McCain, the most vocal supporter of Bush's surge policy: his support has almost collapsed. Yet the Petraeus report is likely to force them to toe the White House line more tightly and in the face of much public hostility. Or it could cause them to go against the White House, following a pro-withdrawal line and opening up huge splits in the party itself. Those chasms are already becoming evident, with some top Republican figures, such as Senator John Warner, already calling for troop withdrawals to begin this year.

But above all the political squabbling will be Bush. No matter what happens, he will be President for all of 2008. And he shows no sign of any significant change of tack. Despite being billed as a watershed moment, the only real prospect of a reversal of Iraq policy will come in January 2009, when a new President walks into the Oval Office. The brutal fact is that there remains no meaningful end in sight for the US involvement in Iraq. Vietnam proved that the difference between when a war becomes unpopular and when it ends can be many years. In July 1967, the public approval rating of the Vietnam war dropped forever below 50 per cent, yet America did not leave Vietnam totally until 1975.

A similar process could be repeating itself in Iraq. Petraeus - as a keen student of history - would probably privately think that a tragedy. In his PhD thesis 20 years ago, he wrote: 'Vietnam was a painful reminder for the military that they, not the transient occupants of high office, generally bear the heaviest burden during armed conflict.'

That is a trenchant analysis. But it was written by the Petraeus of Princeton. The Petraeus of next month is a general playing the highest political stakes of his career in front of the eyes of the world. He is unlikely to be so candid again.

Iraq benchmarks

Iraq has failed to meet all but three of 18 congressionally mandated benchmarks for political and military progress, according to a draft of a Government Accountability Office report to be presented to Congress on Tuesday.

Achieved: The protection of the rights of minority political parties in the Iraqi legislature. It is the only one of eight political benchmarks to have been met, the report says. However, the report does not concern itself with attacks on these parties outside of the legislature.

Failed: In other areas, the political process is judged to have been a failure, including the continued non-passage of legislation on constitutional reform, new oil laws and de-Baathification. Observers say the parliament rarely has sufficient members in attendance to have a quorum to consider legislation.

Mixed progress: On the security front, Iraq has met on two benchmarks. Despite the surge, violence remains roughly at the same levels. However, the number of Iraqi army units capable of operating independently has dropped from 10 in March to six last month.