During the past few weeks newspapers on both sides of the Atlantic have revealed in breathless terms the latest plan to invade Iraq. They have described massive thrusts by armour from all sides; airborne attacks to take out Baghdad; vast seaborne raids. Saddam Hussein, according to one version, will be removed by dissidents inserted into Iraq backed by US Special Forces. Alternatively, Saddam will be taken out in a precision strike.

Civilian officials in the Bush administration have huffed and puffed about the 'leaks', to the amusement of the intelligence and military professionals. 'One thing you can say with an awful lot of certainty,' one told The Observer last week, 'is that there is going to be an awful lot of deception going on over the next few months.'

Deception is one of the oldest of the military's black arts. In the Second World War, the British persuaded the Germans that the Allied invasion plan for the Continent would be through Italy by dumping the body of a bogus officer in the sea carrying false plans for the Germans to find. With the modern media, there is no need for The Man Who Never Was: 'leaks' and 'secrets' are compulsive to journalists.

But the fact of the existence of deception operations is important in itself. It is, in the terminology of these things, a 'combat indicator' - one of the clues that suggest things are fast on the road to getting bloody.

And not all of it is necessarily deception. The military - like all complex organisations - is prone to the same rivalries and disagreements over tactics. Leaking can be lobbying by other means.

There have been other signs and indicators suggestive of the timing of a campaign against Iraq. Manufacturers of cruise missiles and precision-guided munitions in the US have been working overtime to replace the weapons expended in Afghanistan. The American military transport fleet of trucks has been ordered in for rapid servicing. In Chicago last week a freight train loaded with military trucks, painted for desert service, passed through the city. Most tellingly, discreet inquiries have already been made about the availability of tankers to transport the fuel required for war.

Elsewhere, US fighting vehicles in Kuwait have been taken out of the mothballs in which they were left at the end of the Gulf war, while planning cells have been discreetly established in the US, Britain and Germany.

Most curious of all is the apparent lack of activity where you would expect it most. The Pentagon car park, which during the last Gulf war was packed at weekends, is noticeably empty. Senior British officers, including key brigade commanders, are either on leave or about to take it. Cobra, the Downing Street emergency committee, which meets to preside in any war or major crisis, has not yet been staffed up.

The optimistic slant on this is that nothing much is happening. The alternative - as explained to The Observer - is that everyone has been told to take their holidays in August because they might not be able to go later in the year.

The question now appears to be not whether there will be a war, but when. The answer is that in war, as other matters, timing is all. For President George W. Bush that timing will be dictated by the demands of a domestic political agenda. With the economy in the middle of what now looks like a double-dip recession - and his room for manoeuvre on the economic front hobbled by his tax-cut commitments - Bush has been left with only two policies he can sell as a success: the war against terrorism and the war against Saddam.

The war against terrorism is a problematic one. Afghanistan remains a mess. Osama bin Laden and many of his senior lieutenants remain unaccounted for. It is also a war fought in the shadows. Declaring victory would not only be precipitate but dangerous. Which leaves Saddam.

But when to act? Current thinking on both sides of the Atlantic is that Bush will not want to risk a war that does not begin until well into next year, as that would bring him too close to the time when he wants to be engaged in his campaign for re-election. That leaves this winter.

Analysts in Washington are also fast coming to the view that Bush will announce his decision to go to war in good time to allow the Republican candidates for the mid-term elections in November to campaign wrapped in the flag of war. Indeed, some Democratic campaign managers have so convinced themselves of the logic of this timing, and the inevitability of their candidate's defeat, that they are said to have all but given up hope in this election cycle.

And, if anything, it appears that history may look back and judge that it was Saddam last week who set the clock ticking towards war in hinting at a return for the UN weapons inspectors to Iraq.

Conventional wisdom from past confrontations with Saddam has already portrayed his latest 'offer of an offer' as an attempt to buy time. But, far from being dismayed, US and British officials from the pro-war camp are painting Iraq's offer as a serious tactical blunder.

According to this logic, it opens the way for a new inspection crisis and the possibility of a new UN mandate. That mandate, proponents of regime change believe, would inevitably be framed in such humiliating terms that Saddam could not agree to them. It would, they argue, establish the pretext for the coming war.

Finally, there remains the question of what form the war might take. For all the deception and lobbying - for all the boldness of the plans which say the Bush administration may try to do it with a tiny force - the likelihood is that any US-led war against Iraq will be much more traditional than some reports suggest. The key determinants will be guided by the personalities of those involved and a political desire to avoid unnecessary US casualties that could turn public opinion against the war and the Bush administration.

The key is likely to be found in the dogged personality of General Tommy R. Franks, head of US Central Command, US military headquarters for the Middle East, the Gulf and Afghanistan. Those pushing for a more innovative military approach, involving fewer and more mobile troops, have expressed frustration with Franks and his command, which is insisting that any war should be fought in the most careful and conventional ways.