The US President George Bush says he is planning a long-running campaign against what the Americans see as an international terrorist network and the countries that support it.
The first war of the 21st century - as President Bush himself described it - has already begun.
Already there is a deluge of speculation as to what the Americans might do, with options ranging from massive air attacks - possibly against targets in several countries, including Afghanistan - to the insertion of elite forces to take action on the ground.
What is clear though is that the Pentagon is preparing for the long-haul.
Defining the enemy
There are reports of ships being chartered to carry additional fuel supplies to bases in Spain and to Diego Garcia in the Indian Ocean.
There are reports too of giant C-5 transport aircraft flying into Huntsville, Alabama - a major weapons and munitions store - and departing soon after - presumably fully loaded.
So military preparations are moving into high-gear, not just for any immediate strike, but for the operations that may come later.
Certain US arms manufacturers have reportedly been alerted so that they can step up production of key weapons systems should the need arise.
But it is unlikely that there is any campaign plan yet. The nature of the enemy is still to be fully defined.
The US may well take time to lay out its evidence about who is responsible for these attacks to bolster the international coalition that it is building to back military action.
The widest diplomatic support is essential, but practical help may be needed as well.
In some cases this will involve intelligence sharing; maybe even the provision of base facilities.
But America's essential poblem is that it risks embarking upon a new global struggle that has no definable end.
Talking of victory is all very well, but defining what it means in the context of this new age of warfare is very difficult.