Lord knows, it makes no sense to be anything but a pessimist when it comes to the war in Iraq. The occupation remains as bloody and fruitless as the original invasion was fraudulent and needless. But we might detect at least a change, the passing of one phase of this dread conflict into another.

The first and most substantial indicator is the withdrawal, completed on Monday, of British forces to Basra Air Station. Of the 45,000 British troops involved in the original invasion, and the four Iraqi provinces that were once under direct British rule, soon there will be just 5,000, holed up behind the walls of a single airport. These soldiers will no longer live among the people to whom Britain’s UN ambassador promised just last month to bring “a democratic and stable Iraq, at peace with itself and with its neighbors”. Instead they will keep their distance, promising to emerge only “in extremis”. And things will have to get pretty extremis for them to dare to re-enter Basra city again.

Naturally, the government plays down the significance of the withdrawal, insisting it is merely implementing a plan laid out seven months ago by Tony Blair. It is also less forthcoming about the timing. After all, events formed a curious sequence, in which Britain handed over 26 detainees, including members of the Mahdi army loyal to Moqtada Sadr, just as Sadr announced a six-month truce last week. Did Britain cut a deal, to ensure its troops could pull out unhindered in the early hours of Monday morning? And did the Brits have to move now, before any arrangement with Sadr could unravel?

Or perhaps the timing owed more to British anxiety over Washington’s next move. Veteran analyst Dan Plesch of School of Oriental and African Studies (SOAS) wonders if London feared that, should Bush hold firm, even announcing more of his “surge”, Shiite anger in Basra would become uncontainable.

Whatever the calculus, the British presence in Iraq is winding down. All the signs point in one direction: Not toward a full withdrawal at any time soon but to a shrunken, symbolic presence whose prime objective will be to spare the Americans the ignominy of full abandonment by their closest ally. Yet there are signs of a change in the US too. On a surprise visit to Iraq on Monday, President Bush dropped a pointed hint. Speaking in Anbar province, in which Sunni tribal leaders have joined hands with the US to beat back Al-Qaeda, he said “if the kind of success we are now seeing continues, it will be possible to maintain the same level of security with fewer American forces”.

Bush’s hint of a drawdown could well be enough to pacify a few wobbly Republicans. Whatever its motive, Bush’s move suggests the White House now understands its war in Iraq is desperately unpopular and that the way to please the American people is to promise less of it.

This might be the context in which to understand the remarks of the US defense secretary, Robert Gates, who made the midnight flit to Anbar alongside his boss. “I am more optimistic than I have been at any time since I took this job,” he said. At first glance, that might look like proof that Gates is in the same state of denial that characterized his predecessor, Donald Rumsfeld — as if the small triumph of buying off a few warlords in Anbar outweighed all the grief and destruction across the rest of Iraq. But Gates is smarter than that. When he was picked by Bush he was serving on the Baker-Hamilton Iraq Study Group that took such a dim view of the entire Iraq calamity. He was among those who found the situation “grave and deteriorating” and recommended an end to US combat operations in the country. Which means that Gates’s definition of optimism will not be Rumsfeld’s: What would lift his spirits is not a delusion of victory, but an intimation that the end is coming.

This week we also learned that, at an undisclosed location in Finland, 16 delegates from a clutch of warring Iraqi factions met each other to discuss peace.

Now, no one is saying peace is about to break out in Iraq. The hardmen who plant the roadside bombs and plot the marketplace massacres were surely not at that Finnish meeting. But the real significance of those clandestine talks is that it happened at all. It shows that the Iraqis can glimpse a political horizon, a time when the occupation is over and Iraqis have to make their own peace. That time is not now but, it seems, Iraq’s own would-be leaders can at least conceive of it.