The Staggers 2 July 2015 What does potential military action in Syria mean for the Labour contest? Foreign policy will become a defining issue as Jeremy Corbyn declares his opposition to air strikes against Isis. Labour leadership candidates at the GMB hustings on June 9, 2015 in Dublin. Photograph: Getty Images. Sign UpGet the New Statesman\'s Morning Call email. Sign-up In 2013, it was Labour that prevented UK military action in Syria. Should Britain now intervene, as proposed today by defence secretary Michael Fallon, it will be Labour that enables it. After the stunning Commons defeat in the last parliament (the first time a government had lost a vote on a matter of peace and war since 1782), David Cameron will put no motion before the House unless it is certain to command opposition support. It would require just six Conservative rebels for the Prime Minister's majority of 12 to be wiped out. Figures as senior as Crispin Blunt, the chair of the foreign affairs select committee, and Julian Lewis, the chair of the defence select committee, have today expressed heavy scepticism over targeting Isis in Syria. Lewis warned that such action would aid President Assad: "In 2010 the government wanted to remove Assad without helping al-Qaeda or similar groups that subsequently became Daesh. Now we apparently want to remove Daesh but without helping Assad. These two things are incompatible. It is a choice of evils." By contrast, Labour has today signalled its preparedness to suppport military action. Having previously opposed the extension of air strikes from Iraq to Syria, Harriet Harman said that the party would look "very, very seriously" at any proposals to "tackle the growing horror of Isil". In the Commons, shadow defence secretary Vernon Coaker set out Labour's conditions for support: "We all need to be clear about what difference any action would make to our objective of defeating ISIL, about the nature of any action, its objectives and the legal basis. Any potential action must command the support of other nations in the region, including Iraq and the coalition already taking action in Syria." But the decision on whether to support intervention will likely fall to the next Labour leader, who will be announced on 12 September. The prospect of air strikes in Syria means that foreign policy, hitherto almost entirely absent from the debate, will become a significant issue. Jeremy Corbyn has become the first to respond, declaring his opposition to any action: "Terrorist attacks on British citizens will not be prevented by bombing parts of Syria from 30,000 feet. The US is already bombing Syria and this has not stopped ISIL. "Two years ago I voted against bombing Syria when the enemy was the Assad government. I oppose bombing Syria when ISIL is the target for the very same reason – it will be the innocent Syrians who will suffer – exacerbating the refugee crisis. "We need to cut off the supply of money and arms that is flowing to ISIL, some from our supposed allies in the region." Should his three centrist rivals instead take the stance adopted by Harman, Corbyn will be gifted a new dividing line. Liz Kendall, who has called for the 2 per cent defence spending target to continue to be met, is regarded as the most hawkish candidate. Yvette Cooper and Andy Burnham have said little on the subject in the past but are likely to now devote greater attention to it. Though the leadership contest has been treated as a sideshow in recent weeks, the modesty of Cameron's majority means that, in cases such as military action, the new opposition leader will play a pivotal role. As the Prime Minister is all too aware, his room for manoeuvre will be determined by the victor. › Mawkish tabloid fare: how the Amy Winehouse film fails George Eaton is senior online editor of the New Statesman. Subscribe To stay on top of global affairs and enjoy even more international coverage subscribe for just £1 per month!