The political landscape is starting to change around the anti-war movement. The departure of Tony Blair from office much earlier than he would have preferred - itself the result of the catastrophe in Iraq and the consistent campaigning of the movement - creates a new situation.
The British government is already committed to a gradual military withdrawal from Iraq, where the troops now seem to be serving no conceivable purpose even in the government's own terms. Gordon Brown may decide to accelerate this process. Likewise, he may announce a clear intention to set up an inquiry into the circumstances under which the country went to war in 2003.
While Brown cannot be seen as anything other than entirely complicit in all the decisions around the war, he will not immediately become a subject of the same degree of public opprobrium as Blair. It is the latter's lies, and consistent contempt for the British public, expressed in his willingness to back George Bush time and again over the views of those to whom a British prime minister is nominally accountable, that has enraged millions.
One danger is that this could breed an element of political complacency - a feeling that, after getting on for six years, the work of the Stop the War Coalition is in sight of completion. In fact, there is little sign that the "long war" launched by the US in 2001 (arguably in 1991, with the first Gulf War) is coming to an end. Instead targets and priorities are shifting.
Three issues require particular attention. The first is a genuine and complete end to the occupation of Iraq. British troops may be on the way out, although doubtless not before many more have died in vain. It would also seem that the US "surge" in and around Baghdad is failing - both militarily in breaking the insurgency, and politically, in creating the space for a stable pro-US governing alliance to emerge.
Under these circumstances, political pressure in the US for troop withdrawal will surely intensify. However, this will not mean an end to the occupation, but rather its concentration on several mega-bases presently under construction across Iraq to provide a permanent US military presence geared towards domination over the entire region.
That, of course, would be a sign of further wars. An end to the occupation must mean the total withdrawal of all US and British forces and bases.
Second, the occupation of Afghanistan should come under sharper focus. If anything, the government in Kabul is even more politically bankrupt and US-dependent than the one in Baghdad, and the military position of British troops even less promising. While an occupation of Afghanistan cannot have the global strategic significance of the seizure of Iraq, it is failing by every measure - indeed, it seems to be allowing the Taliban to recover political support it might otherwise have lost.
And, of course, it is evidently unwelcome to the great mass of the Afghan people, who should enjoy the same right to self-determination as peoples everywhere. A cursory reading of history shows that they are firm in asserting this right. The British general staff appear to imagine that it can be fourth time lucky for an occupation of Afghanistan. The anti-war movement needs to tell them they are wrong before many more lives, Afghan and British, are needlessly lost.
Finally, the danger of the war being extended to Iran needs to be highlighted. How realistic is this, in light of the huge setbacks to US strategy in Iraq? Certainly, the Washington elite is now divided on the question and the "realist" wing appears to be ascendant.
However, detailed reports in the New York Times and elsewhere make it clear that US vice-president Dick Cheney is still pushing for an attack on Iran before their term of office elapses - perhaps as early as next spring. So far Cheney appears to have won most of the foreign policy battles within the administration.
Furthermore, influential senator Joe Lieberman has called for military raids against Iran as reprisals for alleged Iranian support for Iraqi insurgents, and all the main candidates for the Democratic Party presidential nomination are falling over themselves to take a tough "all options on the table" line with Iran, to balance their quit-Iraq rhetoric.
There is a logic in this. A categorical defeat in Iraq would leave the US in a dreadful strategic position in the Middle East, not least because it would leave Iran ascendant. It would not be much of an overstatement to say that the whole post-1991 drive to impose a US-dominated world order would be in ruins. So regime change in Iran, by force if necessary, may seem like a pre-requisite for leaving Iraq.
So these are the tests Gordon Brown will face-genuine independence for Iraq; an end to the Afghan adventure; and no support (political or military) for aggression against Iran. The Stop the War Coalition's test is to ensure that he gives the right answers.
Andrew Murray is national chair of the Stop the War Coalition.