Britain's decision has strengthened the will of insurgents to carry on, writes Michael Jansen.
The announcement by British prime minister Tony Blair that 20 per cent of Britain's troops in southern Iraq will be withdrawn by May and other significant withdrawals could be concluded by the end of the year had instant repercussions in Iraq.
By conveying the impression that Washington's allies are abandoning a sinking ship, Britain has strengthened the determination of militias, resistance groups, and foreign jihadists to carry on with their struggle in the expectation that the British pull-out is likely to sap the will of the US public to sustain the military campaign in Iraq.
Although Mr Blair said he would be pulling out only 1,600 of 7,100 troops, Britain is the second largest contributor to the international force after the US, and British troops account for half of non-US foreign soldiers serving in Iraq.
Furthermore, Mr Blair is not the first or only leader in coalition countries to adopt this line. South Korea, with the third largest contingent of 2,300 troops, is pulling them out this year. Poland has announced the withdrawal of its 900 soldiers by the end of 2007, and Denmark will repatriate its 460 troops by August.
Since developments are closely followed by insurgent and militia intelligence operatives via the internet and satellite television, the morale of US opponents in Iraq and elsewhere in the Middle East will be greatly boosted by the shrinkage of the coalition.
They realise this will ratchet up pressure on president George Bush to, at the very least, set a timetable for withdrawal, although he contends that the US cannot depart until Iraq is stabilised. Once a timeframe for the departure of US forces is announced, insurgent and militia leaders can plan their military moves with the aim of securing political advantage while withdrawals take place.
For US antagonists, news from the US home front is also positive. The Democrats are fighting Mr Bush's 21,500 troop "surge" and insisting on an early exit for most of the 35-37,000 troops now deployed in Iraq instead of continuing the build-up until the deployment has reached 53,000.
Now that Britain has announced its exit strategy, its diminishing troops in southern Iraq can be expected to adopt holding tactics in the area the UK has failed to stabilise over the past four years. Britain's aim will be to impose a minimum of order without confronting the Shia parties competing for power or criminal gangs who operate freely there. In the absence of constant military pressure on gangs and guerrillas, the south will soon sink into anarchy and chaos.
This will make it easier for renegade Shia militia elements, key targets of the current US "surge", to find sanctuary in the south until they dare to return to the streets in central and northern cities and towns. This will defeat the counter-insurgency campaign.
The running down of the British contingent, which remains under overall US command based in the capital, will weaken the tenuous link between the outer regions and the centre. Basra and and the south do not respect the writ of the central government in Baghdad. Provincial governors and local tribal and faction figures are largely independent. Local police are under the control of the Fadhila party, an offshoot of the movement headed by radical cleric Moqtada al-Sadr, while national police are dominated by the Badr Corps militia of the pro-Iranian Supreme Council for the Islamic Revolution in Iraq (SCIRI).
The Sadrist Mahdi Army militia, seen by Washington as a main destabilising force, also has a strong presence.
Since these elements have expelled most of Basra's Sunnis and Christians, there is little sectarian conflict but the area remains volatile and violent. No national force is capable of halting the decline in security. Iraqi army units are also packed with elements from the Badr Corps, the Mahdi Army and Fadhila.
The troops are poorly trained, ill-equipped and suffer from a high rate of absenteeism.
No combination of Iraq's security forces can replace the British troops. The withdrawal of Denmark's contingent, deployed within the British area of operations, will leave Dhi Qar province at the mercy of highwaymen and militia fighters.
Increased insecurity in the south will make it all the more difficult for Iraq to continue exporting oil from its southern terminal, which has been the main outlet for the flow of crude to customers as insurgents frequently cut pipelines carrying crude through Turkey to the Mediterranean export terminal. Militias and criminals are likely to increase oil smuggling, which is already funding their activities.
One analyst pointed out that deepening unrest in the south will endanger the lines of supply for US and other forces. These lines run from Kuwait northwards along the Tigris and Euphrates river valleys to Baghdad. Instability will hugely complicate the eventual withdrawal of US troops and their heavy equipment.
The draw down of British and other forces from the south will leave a political vacuum into which Iran will move. Iranian influence, which is already very strong in the south, is certain to creep northwards to the Shia Sadr City district of Baghdad, increasing the likelihood of clashes between the pro-Iranian Badr Corps and the anti-Iranian Mahdi Army.
Meanwhile, Iraqi nationalist and Sunni fundamentalist insurgents, which are constantly improving their operational capabilities and adopting new weapons, have already begun to step up their attacks on US and other allied forces with the aim of undermining popular support for the war in their home countries.
During the last six months the insurgents doubled the fatality rate for US soldiers to 85 a month. By proclaiming that the withdrawal of British troops will begin this spring, Mr Blair signalled that he is preparing to jump from the sinking Iraqi ship , making it all the more difficult for Mr Bush to stay on.