More so than any other since the toppling of Saddam Hussein, 2008 is set to be a make-or-break year for Iraq.
There is a window of opportunity, which needs to be exploited
The country ended 2007 on a high.
The last third of the year saw a dramatic improvement in the security situation in many of the most troubled areas, including much of Baghdad.
The number of attacks of all sorts, and the ensuing casualties, showed a sustained decline.
But none of the threats to Iraq's stability and future has been definitively defeated.
None of the factors feeding into the improvement is irreversible.
Window of opportunity
And there have been many warnings that if the security gains are not underpinned by political and economic measures, they risk being squandered.
So there is a window of opportunity which could close sharply if it is not exploited.
You're certainly not going to hear from me that al-Qaeda is defeated and that victory is at hand
If things go well, 2008 could see the security improvement consolidated further, with revitalised Iraqi army and police forces taking the lead. The centre could be strengthened by nation-building legislation and political reconciliation, and the new stability could give birth to an economic surge that would add to the positive dynamic.
But that vision could turn out to be a pipe dream - it is not hard to imagine a much grimmer scenario, such as:
- bickering Iraqi politicians fail to rise above their differences and agree vital legislation, which is already months behind schedule and would weld the country together
as US forces start to thin out to pre-surge levels by July 2008, al-Qaeda begins to make a comeback
Sunni "local security" forces established by the US, clash with Shia militias, which laid low until the American grip loosened
Iraq disintegrates into sectarian strife, perhaps descends into unequivocal civil war.
Prime Minister Nouri Maliki has said that 2008 will be the year of reconstruction and development, following what he says is the defeat of al-Qaeda and terrorism.
The British-trained Iraqi police force has grown but is compromised
Few others are so starkly optimistic, least of all the Americans, whose claims are more modest and qualified.
"You're certainly not going to hear from me that al-Qaeda is defeated and that victory is at hand," said the US ambassador, Ryan Crocker.
"Al-Qaeda has shown an extraordinary persistence, and they are persisting now, although clearly, their abilities have been badly damaged."
The past 12 months saw a double body-blow dealt to al-Qaeda and the Sunni-based insurgency, which had many strands.
The US troop surge, built up over the first half of 2007, saw the Americans directly and more proactively tackling the militant Islamist groups linked to al-Qaeda under the umbrella of the "Islamic State in Iraq".
At the same time, a number of the more Iraqi nationalist insurgent groups, such as the 1920 Revolution Brigades and the Islamic Army in Iraq, turned against the al-Qaeda radicals and joined Sunni tribal leaders in urging their followers to join the Americans against them.
The result: by the end of the year, around 80,000 Sunni youths were on the US payroll as local guards looking out for al-Qaeda infiltrators.
This had a big effect in pacifying troubled Sunni areas such as Anbar province and parts of Baghdad.
Moqtada Sadr told his Mehdi Army to halt hostilities for six months
But the campaign is unfinished, with frequent violence in areas to the north of the capital, and displaced Islamist radicals surfacing at Mosul in the far north too.
Many of the Sunni vigilantes have Shia blood on their hands, and their emergence as virtual militias has raised fears of future sectarian battles if things go wrong.
On the Shia side of the equation, the order given in August by the Shia cleric Moqtada Sadr to his Mehdi Army militia to halt hostilities for six months had a big effect in reducing violence.
That decision may have been influenced by Iran, which, also in August, promised Prime Minister Nouri Maliki that it would stop supporting Shia militias and put its weight behind the Baghdad government.
Starting in March, Iranian and US officials held several rounds of direct talks on Iraq, a dialogue that is set to continue.
US commanders have said there are signs of a drop in help from Iran for radical Iraqi militias, and also in the flow of Arab fighters coming across the border from Syria.
If the current signs of a slight thaw in Washington's relations with Tehran and Damascus are sustained in 2008, that would benefit Iraq.
But it will not be an easy year.
In the south, British forces have already handed over security control to Iraqis and taken up a background role, which will see UK forces cut by half to a mere 2,500 or so in the spring.
In Basra and elsewhere, much power remains in the hands of Shia militias vying for supremacy and control of oil resources.
When the US surge ends, troop levels will return to early 2007 levels
The state faces a tough struggle to impose its authority, which it must do if Iraq is to hold together.
That highlights the weakness at the centre. Politicians, divided largely on sectarian and ethnic lines, have so far failed to agree on a shared vision of the country's future shape, and to pass legislation to consolidate it.
While the Iraqi army and police have been built up in numbers, there are doubts about whether they are up to filling the vacuum as US forces draw down. The police in particular are riddled with militia influence.
By July, the "surge" will be over. US troop levels will be back to the 130,000 or so who were there early in 2007, and pressure will be mounting for more to go home.
This is another reason why 2008 will be a crunch year for Iraq - the year in which the balance will tilt one way or the other.
Whichever way it goes, for better or for worse, Iraq will be a very different place in a year's time.