The outlook for Iraq looks stormy, following a string of devastating attacks and assassinations in the run-up to the transfer of power to an interim government. BBC News Online examines the military landscape awaiting Iraq's new rulers after the handover.
The US came to Iraq looking for banned weapons - but found none
The invasion of Iraq was inspired by claims about Saddam Hussein's banned arsenal; the occupation of Iraq is overshadowed by concerns over the disbanding of his army.
With coalition forces and Iraqi security services battling an insurgency, correspondents say last year's decision to dissolve the defeated Iraqi army may have been the single biggest mistake of the occupation.
The 400,000 Iraqis fighting for Saddam Hussein made up what was reputed to be one of the most formidable forces of the Middle East.
They have been replaced by about 160,000 soldiers from a coalition of more than 30 countries.
America's 138,000 troops form the backbone of the force.
They are supported by smaller groups of soldiers from countries as diverse as the UK, Italy, Poland, Ukraine, Thailand, Mongolia, Albania and Azerbaijan.
Resisting them is a range of fighters almost as diverse as the coalition itself.
Attacks have been mounted by Sunni and Shia militants and militiamen, foreign jihadis perhaps inspired by al-Qaeda, opportunistic criminals, die-hard Saddam loyalists, as well as those who claim to be no more than patriotic freedom fighters.
The violence appears to be worsening as the coalition prepares for the handover to an interim Iraqi government.
The insurgency is also hampering efforts to build a new Iraqi security apparatus that could eventually relieve the foreign forces of their duties.
Many of these problems could have been prevented if Saddam's military had been preserved, analysts say.
Many obstacles lie ahead on the road to Iraqi sovereignty
The decision to shatter that monolith scattered unemployed gunmen across Iraq, many of them nursing a grudge against the coalition.
It also destroyed a ready-made security apparatus of the kind the US is now desperately trying to build.
According to the more optimistic estimates, the coalition has so far managed to partially train two-thirds of the 260,000 security personnel it believes Iraq needs.
But our correspondent says serious doubts have emerged over whether the new Iraqi forces are ready - or willing - to undertake combat operations against a committed local opposition.
It has become clear recently that Iraq needs more foreign troops - and for longer than originally anticipated.
However, a broad consensus on sending an international force to Iraq continues to elude the UN and Nato.
Moreover, US President George W Bush wants to avoid pouring more American soldiers into the war zone - an unpopular move with the voters whose support he needs this year and with the military planners who are complaining of overstretch.
Correspondents say the likeliest source of re-enforcements is Britain - its 8,000 soldiers already make it the largest non-US force in the coalition.
That deployment could soon double in size.
British soldiers, operating out of Basra, currently command the south-eastern sector of Iraq.
More troops would allow the area under their command to expand to include the south-central sector, home to the Shia holy cities of Karbala, Najaf and Kufa.
The British are also keen to bring to Iraq the moveable command facility known as the Arrc, or Allied Rapid Reaction Corps, according to the BBC's defence correspondent, Paul Adams.
The Arrc currently rests in Germany, as part of the Nato structure.
Poland could also provide a possible boost to troop numbers - it is already the third-largest non-US force in the coalition, with 2,400 soldiers currently in command of Iraq's south-central sector.
Ukraine is another potential candidate - its 1,700 soldiers are also in the south-central sector, operating under the Poles.
South Korea has promised to send 3,000 troops to supplement the 465 it already has in Iraq. No date has been set for their departure but their destination is likely to be the northern town of Mosul.
The other countries in the original list of top 10 non-US coalition armies are not expected to make significant changes to their troop numbers.
Italy and the Netherlands have 2,700 and 1,400 troops respectively in Iraq, operating under British command in the south-eastern sector.
Spain, which had 1,300 soldiers in the south-central zone, withdrew its contingent earlier this year.
Of the remaining nations in the coalition, few have more than 500 personnel in Iraq, many have less than 100.
The smallest contributor is Moldova, which despatched a squad of 24 to register its support for the "war on terror".
The US is likely to retain overall command of the three sectors in northern, north-eastern and western Iraq, as well as in Baghdad.
Insurgents and coalition soldiers may account for most of the violence in Iraq - but they are not the only gunmen on the landscape.
Many of Iraq's ethnic groups command their own militias
Any political solution to Iraq's military crisis must take account the many militias that, at present, are neither fighting nor actively aiding the coalition.
The 10,000-strong Badr Brigade is one of the most important - an armed extension of the Shia political party, Sciri.
The Islamic Dawa party commands its own militia, estimated to have 1,500 gunmen.
There are also some 50,000 Kurdish peshmerga guerrillas in the north of the country, who cut their teeth against Saddam's army.
Some US officials hope these disparate forces will eventually unite under the umbrella of a new Iraqi army.
They cite with hope a corner of the country where an all-Iraqi force has already taken charge - Falluja.
Coalition forces laid siege to Falluja in April, after television pictures showed the city's inhabitants celebrating over the charred remains of ambushed American security guards.
A long and bloody stalemate ensued. Concern mounted over the runaway civilian death toll.
The strength of the resistance in Falluja came as a surprise
The apparent resilience of the resistance also surprised the US. But Falluja is in the so-called Sunni triangle, a city with a tradition of military service, hard hit by the disbanding of the old Iraqi army.
After a unit from the new Iraqi army refused to support the siege, the Americans hit upon a novel solution.
They enlisted a general from Saddam Hussein's old army to round up a 600-strong force of local former soldiers to take control of the city.
The Americans stepped back and the new force stepped in.
On the streets of Falluja, its arrival was hailed as a victory.
Many of the men in the new force were believed to have been insurgents, who had simply traded their red-checked headscarves for the brown uniform of the Falluja Brigade.
It was a hasty solution, says the BBC's Paul Adams, and an imperfect one - Falluja is now a no-go area for Americans.
He warns that the real test of the solution will come when the new Iraqi government tries to extend its writ into the city.
If it succeeds, the Falluja formula will be hailed as an innovative way of correcting a cardinal error of the occupation - the summary disbanding of the Iraqi army.
If it fails, the formula will resemble not so much a settlement, as a surrender.
Figures for troop deployments provided by Globalsecurity.org and The Brookings Institution. Numbers do not include troops stationed at sea and in countries neighbouring Iraq