As the debate intensifies around whether to hold a Commons vote before any action in Syria, and then whether MPs should vote for or against such action, attention turns to the Parliamentary arithmetic.

In 2013, the Coalition Government suffered the worst defeat on foreign policy in modern times, over the question of whether to carry out strikes against Assad in response to his use of chemical weapons on Syrian civilians. We all remember how Ed Miliband’s Labour Party had promised to support the Government, only to change tack – shamefully – at the eleventh hour. But what’s often forgotten is that 30 Conservative MPs also rebelled against Cameron on the issue – making all the difference in a vote which the Government lost by just seven votes.

If there is a new vote, on a new motion albeit on a similar topic, then it could well come down to how many rebel MPs there are on each side of the House. The Government has no majority of its own, while foreign policy is a specifically fraught area of tension between Jeremy Corbyn and many of his backbenchers.

Some of the 2013 Conservative rebels (like Sarah Wollaston) have signalled their minds have since changed on the issue, while others (like Steve Baker) haven’t commented publicly but are now bound by collective responsibility, but some (like John Baron) have restated their continued concern about involvement in the Syrian civil war. Given that seven Conservative MPs even voted against bombing ISIS in Syria, it seems likely a new vote on action against Assad would bring a Tory rebellion on some scale, but perhaps less than the 30 of 2013.

Over on the Labour benches, there are some signs of consciences wrestling to assert themselves against fear of Corbynite vengeance.

John Woodcock – long since past the point at which it was even worth trying to hide his disdain for the Labour leadership – has called in the Evening Standard for his colleagues to ‘rise above the excuses and diversions which emanate from the shadow front bench whenever there is a crisis.’ Woodcock appears nailed on to vote for action, whatever his whip might say, but it’s questionable whether his support might encourage or deter less committed colleagues by association.

At the other end of the spectrum, Kate Osamor, the Shadow International Development Secretary, gave an interview to the House Magazine in which she said Assad “needs to be removed” if his government’s responsibility for the Douma attack was proven – only to promptly beat a retreat and try to claim that the quotes she gave “simply don’t represent my views”. The reporter who interviewed her rightly stands by his story, but nonetheless Osamor’s about-turn illustrates the fact that Corbyn’s personal authority and his grassroots following still hold considerable sway, meaning that the application of the Labour whip against action will successfully compel some of his MPs to swallow their principles. After all, they’ve done so plenty of times before.

Still, there are evidently some who differ drastically from Corbyn’s world-view. When he granted a free vote on bombing ISIS in Syria in 2015 (albeit a ‘free vote’ for which some of his supporters still called for dissenters to be punished) there were 66 Labour MPs who voted in favour of action, famously led by Hillary Benn. Being whipped to vote against might make a difference to many of them, but not all. Chris Leslie, Pat McFaddenMary Creagh, and Alison McGovern, for example, have spoken publicly about regretting their vote in 2013, which hints that they could potentially vote differently in a similar scenario today.

Still more Opposition MPs, like Wes Streeting, say they are undecided – and by implication could therefore be persuaded if the Government were to put a sufficiently compelling case. So, while the arithmetic is always tight in a hung parliament, and there could well be Conservative rebels, the Government could yet secure a majority if it wins the support of enough Labour MPs.