The House of Commons schedule will be cleared today for a crucial ten-hour debate on British air strikes against the Islamic State terror group.
The long parliamentary session will culminate in a vote in which unionist votes are likely to be pivotal in securing backing for David Cameron’s plan to escalate UK military involvement in Syria.
The prime minister had said that he would not risk a vote unless he was confident of victory so it appears that his aides believe there is now enough support.
What is happening is extraordinary on two counts. First, both the public and elected politicians are as confounded as they have ever been (since the advent of mass democracy) as to whether or not to become embroiled in a war. There is near unanimity that Islamic State are depraved and deserving of overthrow, but there is huge uncertainty as to how to achieve this, with the chaos in Iraq and Libya fresh in the memory.
Second, the leader of the Labour Party has been comprehensively outmanoeuvred by both his own MPs, who think Jeremy Corbyn is an electoral liability, and by the government.
It is not that opposition to air strikes is obviously wrong and foolish. That there is such widespread uncertainty illustrates that there are plausible arguments against intervention.
The problem is that Mr Corbyn has made excuses for one violent group after another – such as Hamas and the IRA – yet he is always adamant that western violence is wrong. He rarely seems to show the same moral clarity against terrorists.
This has hardly helped his case with unionist MPs. Both the DUP and Ulster Unionists seem to have come round to the cautious position that a group that carries out massacres such as that which happened in Paris last month cannot be allowed to retain large swathes of territory untrammelled by the nation it attacked, France, and her allies.
This is no vote for ground troops, but for extended bombing missions. It will be no panacea. But Paris showed that we cannot easily stay entirely on the sidelines of this global drama.