The deployment by the United States of slow-flying AC-130 gunships in Afghanistan yesterday reflects the confidence of American commanders that the aerial assault has largely eliminated Taliban ground defences.
It also reflects their belief that the bombardment is starting to flush al-Qa'ida and Taliban fighters out into the open, turning them into "emerging targets" in the words of Donald Rumsfeld, the American Defence Secretary.
But Mr Rumsfeld will not say more than that in public. He refuses to discuss operations by US commandos and special forces units, although these units are believed to have been inside Afghanistan before the bombing began, carrying out reconnaissance missions and providing ground guidance for many of the air attacks.
On Monday, Mr Rumsfeld gave a rare indication of their presence, acknowledging that intelligence information had improved "both from the air and on the ground" enabling the much heavier air strikes of this week. "Troop concentrations have been attacked every day in the last three or four [days],'' he said, adding that for Taliban forces dug in north of Kabul, "that's not going to be a very safe place to be".
From the outset there have been two schools of thought in the US military high command. One wants to begin ground operations as quickly as possible, aware of the political problems the much more visible air campaign is causing with some of Washington's allies in the Muslim world.
The other, however, believes that until the precise whereabouts of Osama bin Laden and his followers are established, even the most experienced commando units would be at unnecessary risk. They point to the heavy losses sustained by Soviet special forces during Moscow's futile 10-year war in Afghanistan – despite a pro-Soviet government being in power in Kabul.
Mr Rumsfeld's acknowledgement that intelligence information had improved may portend a closer link-up between the US military and the opposition Northern Alliance, which Washington has been keen to prevent from capturing the capital.
Mr Rumsfeld, however, did not say whether special forces units were turning directly to the hunt for Mr bin Laden himself – probably because his senior Pentagon advisers are divided on the subject.
Where Mr Rumsfeld stands in the arguments over how the war should be conducted is not clear. He is a man famous for his impatience with bureaucracy and was said to be livid at the chain-of- command tangle which reportedly threw away an opportunity to kill Mullah Mohammad Omar, the Taliban leader, on the first night of bombing on 7 October. It is also said that he wants to bring the special forces central command, currently in Tampa, Florida, to Washington, under the direct control of himself and President George Bush.
The Defence Secretary has repeatedly stated that the war against terrorism will not be won by bombers and cruise missiles – implying that he wants to move to the ground phase as soon as possible. But in the next breath he warns that this war will not be quickly won, and that Americans must brace for the long haul.
Political and diplomatic factors further complicate the equation. As it struggles to settle the shape of a post-Taliban Afghanistan, Washington has been extraordinarily careful not to hand victory to the Northern Alliance while there is no obvious successor in place. Such an outcome would not only be unacceptable to Pakistan, but almost certainly guarantee more chaos inside the country.
Once an outline future government has been agreed however, it will be easier to go all out for victory on the ground, working with the Northern Alliance and breakaway elements of the Taliban in the south of the country. This consideration also has a major bearing on whether US ground operations are launched from temporary bases inside Afghanistan, or from outside – most likely the aircraft carrier, USS Kittyhawk, in the Arabian Sea.
What is unarguable is that Mr Rumsfeld's reputation has soared since the attacks on New York and Washington. Before 11 September, his removal from the Pentagon was being widely forecast. But as one general told The New York Times last week: "He was spiralling down as Secretary of Defence, but he's a damn fine secretary of war."
All of which strengthens his hand for the post-war reorganisation of the military which Mr Rumsfeld is determined to push through. Well before 11 September, he had pressed for a streamlining of US forces, arguing that old style "symmetrical" wars belonged to the past, and that more nimble forces were needed to fight the less predictable wars of the future. The terror attacks had only increased the urgency of change. He said: "For the military, it means two questions: How can you get arranged to deter? How ought you to be arranged to pre-empt, if you see it coming before it happens?"