The Obama administration is going for broke in the case of Bradley Manning, the perpetrator of the biggest leaking of classified documents in US history - but at the end of the first week of the trial, it seems that Washington is flogging a dead horse.

The pint-sized Manning arrives at court some mornings sandwiched between two seemingly enormous military guards, and so looks more like a schoolboy being hauled before the headmaster.

And arguably he has given the ''headmaster'' what he wants - in admitting that he leaked the 700,000-plus diplomatic and military papers he has pleaded guilty to about half of the charges against him and says he'll do 20 years in jail.

Nope. The prosecution is pressing ahead, determined to see Manning convicted on the charge that he ''helped the enemy'', which is punishable with death, but in the case of the former military intelligence analyst, the prosecution says it would settle for life behind bars with no chance of parole.

The question then, is why?

Media lawyers see it as an attempt to establish a chilling precedent - a warning to all would-be leakers of national security information that they would be risking lengthy solitary confinement, as endured by Manning, and the prospect of death or spending the rest of their life in jail.

Describing as ''ruthless'' the administration's pursuit of "anyone who releases any information or talks about government malfeasance or the abuse of power," former US Army colonel and diplomat Ann Wright told Fairfax Media: "The government wants to put an end to whistleblowing."

The ''helping the enemy'' charge is under the 1917 Espionage Act - used just three times in its first 92 years, but used six times in Obama's first term as president.

Manning's court martial coincides with a realisation by many Americans of two surprising aspects of the Obama presidency - it is intensely secretive and more zealous than any of its predecessors in guarding that secrecy.

Here, the government appears to be relying on a level of public apathy that dovetails with the military notion that, more often than not, the military does not have to explain itself.

None of this sits easily with the notion that this is the President who first campaigned to be Commander-in-Chief telling Americans that he would be the whistleblowers' new best friend and that he would preside over ''a new era of open government''.

Oddly the US media is not hugely interested in the Manning trial. Reports on the opening could not command page one in The New York Times or The Washington Post, despite both newspapers incurring the legal wrath of the Nixon administration in the previously most celebrated case of leaks and government secrecy - the Pentagon Papers sensation of 1971.

Back then Washington pursued the publishers - which were newspapers. And newspapers were critical in publishing the contents of Manning's data dump, but this time there was a vital middleman - the WikiLeaks anti-secrecy entity, founded by Australian Julian Assange.

The prevailing atmosphere might be expected to put air beneath the wings of the Manning defence - the Obama administration is under fierce attack because of overly zealous snooping by the taxman; its rottweiler-like pursuit of leakers, which includes seizing reporters' phone records and describing the conventional practice of journalism as breaking the law - either by conspiring with a leaker or by aiding and abetting them.

In the same vein, the trial proceeds against a backdrop of bipartisan political anger at the shortcomings of the military justice system in dealing with endemic sexual abuse and harassment across all arms of the services.

For all that, this trial and the aggressive posture of the White House are remote from the balance struck in the Pentagon Papers case.

On the one hand, there was Justice Potter Stewart: "It is elementary that the successful conduct of international diplomacy and the maintenance of an effective national defence require both confidentiality and secrecy." And on the other, Justice Hugo L. Black: "The guarding of military and diplomatic secrets at the expense of informer, representative government provides no real security for our republic."

The trial itself is an exercise in military-minded secrecy - reporters and the public are made to jump through hoops merely to be present; and for as many as one-third of the prosecution witnesses, the press and spectators will be ordered out of the court; photographers outside the court are blocked from getting images of Manning; photographs and documents tendered in court are withheld, to be released seemingly at the whim of the court or its staff.

And on the opening day of the trial, here, in the land of free speech, US Army guards at the court ordered Manning supporters to turn their ''truth'' T-shirts inside-out before allowing them into the tribunal.

In the Manning case, Military Judge Colonel Denise Lind gives away little. Some thought a smile creased her face when she addressed the defendant on the opening day, but Manning supporters are more struck by the fact that she had allowed just one of about 100 defence motions in proceedings to date.

However, she had issued a preliminary ruling in which she deemed the extent of any damage caused by the Manning leak to be immaterial.

Government spokesmen, including former secretary of state Hillary Clinton, would have us believe that the sky fell in the aftermath of the staggered leaks, but when the rhetorical angst was put to one side, it seemed that the consequence of the leaks was limited to a hefty dose of embarrassment in Washington.

No American supporter of democracy could complain about their purported role in firing up the anti-regime resentment that fuelled the Arab Spring revolutions and by its own admission, Washington has not been able to link the death of any American or any of their Iraqi and Afghan helpers to the Manning leaks.

The prosecution has marshalled a small army of witnesses - more than 140. But some of the first dozen or so spoke well and constructively of Manning or offered insights that complicated life for the prosecution more than they did for the defence.

"Very neatly organised, very categorised - I've seen a lot of soldiers but not to his level," said Chief Warrant Officer Hondo Hack, describing Manning as one of the best soldiers to work under his command.

There was a major embarrassment for the prosecution when one of Manning's senior analyst colleagues revealed they had not been warned about websites that al-Qaeda and the other insurgent groups used as sources of information.

"It is general information that they go on all sorts of websites," Captain Casey Fulton explained before rattling off a list that included Facebook and Google - but not WikiLeaks.

It remains to be seen if Fulton's evidence will be deemed to be above or below the bar set by the judge when she ruled in a pre-trial decision that the prosecution must show that Manning had ''actual knowledge'' of himself ''actually giving intelligence to the enemy'' through ''a third party, an intermediary or in some other indirect way''.

In particular, the prosecution had to show that Manning had ''a general evil intent'' and to have been aware that he was ''dealing, directly or indirectly, with an enemy of the US''. In this the judge seems to agree with Bill Keller, a former managing editor of The New York Times, when it was one of several newspapers worldwide that teamed up with WikiLeaks to publish the Manning leaks.

This year Keller was withering when he wrote of the prosecution: "If Manning's leak provided comfort to the enemy, then so does every news story about cuts in defence spending, or opposition to drone strikes, or setbacks in Afghanistan."

Did Manning ever say that he wanted to ''help the enemy'' - "not in those words, no," said the convicted hacker Adrian Lamo, to whom Manning had first owned up to the leaking and who, within 24 hours, had dobbed him in to military intelligence.

And surely there was some evidence of Manning's terrorist tendencies on his computers? Mark Johnson, a forensic digital examiner on contract to the US military, said that none of the material found on the computers related to terrorism or "indicate a hatred of America".

Former army colonel Ann Wright works with the Bradley Manning Support Network but is not privy to the defence's deliberations, said of the week's evidence: "No one has been able to link Manning to wanting to get stuff to Osama bin Laden."

But she took little comfort from the seemingly powerful testimony, saying: "I expect the judge will find him guilty - and then there will be appeals that will last for years. The thinking in the military establishment is if she doesn't put him away for a long time, then she's not doing her job."

Intriguingly, the government is limiting its sense of the potential audience for the WikiLeaks material to terrorists - ''the enemy''. Observing the trial, American Civil Liberties Union lawyer Ben Wizner found this striking, citing the Abu Ghraib torture pictures as he told The New York Times: "Sometimes what may be helpful to the enemy is also indispensable to the public in a functioning democracy."