In the summer of 2013, David Cameron’s foreign policy received a blow from which it has not yet recovered.  First, he urged Barack Obama to launch strikes against Bashar al-Assad after the latter’s regime used chemical weapons.  The President was eventually persuaded.  But the Commons refused to back the Prime Minister up.  Cameron was humiliated before our most important ally.

Then, the Prime Minister’s target was the Assad regime.  Now, it is ISIS – which itself opposes Assad (though the picture is more complex than this: indeed, the two have an interest in propping each other up).  Conservative MPs weighing whether or not to vote for air strikes against Syria this week may well view this change as evidence of flawed strategic thinking.  They might note that Britain’s contribution to bombing will be relatively small.  They may take the point that Nadhim Zahawi makes on this site today – namely, that bombing alone is not enough.  Peace in Syria depends on troops on the ground and a broad-based political settlement.  Finally, they will be very wary of military intervention abroad, in the wake of Libya, Afghanistan and the Iraq War.

But if they ponder deeply enough, they will swiftly see that any comparison with those last three actions does not hold.  In those cases, Britain aimed to overthrow or support governments.  In this one, all that is proposed is that bombing does not stop at a border that no longer exists – the Sykes-Picot line that separates Iraq from Syria.  We are already bombing ISIS in Iraq.  It makes no sense not to do so in Syria too.  The sending-in of ground troops has been ruled out.  The threat of ISIS terror is here in Britain already, and strikes against ISIS in Syria are unlikely to make it significantly worse.  And we should not be frightened off by Islamist extremism in any case.

Above all, our allies want us to join them.  We are being asked to stand with France in her hour of need.  What we can achieve may be limited, but it would be unreasonable to refuse.  And the disposition of Tory MPs should be towards helping their leader out.  They should back him in the lobbies – and leave rebellion, division and chaos to Jeremy Corbyn and his disintegrating Party.