When Jeremy Corbyn offered Labour MPs a free vote on air strikes in Syria, he arrived at the position that most of his colleagues had long regarded as inevitable. What stunned both supporters and opponents of military action was the tortuous route by which he did so. Corbyn’s failed attempt to whip his party against air strikes left “deep wounds”, shadow cabinet members say, and revealed him as a leader caught between co-operation with his MPs and confrontation.

After David Cameron signalled his intention to seek Commons approval for military action, Corbyn could have made a principled and pragmatic case for a free vote. “Something so fundamental as the deployment of armed forces”, he declared in 2013, should never be made an issue of “party loyalty”. The support of senior frontbenchers, such as the shadow foreign secretary, Hilary Benn, and the deputy leader, Tom Watson, for air strikes persuaded many that a free vote was not merely desirable but essential. It was on these grounds that the shadow chancellor, John McDonnell, Corbyn’s greatest parliamentary ally, consistently argued for one.

But rather than adopting this stance, the Labour leader sought to turn his shadow cabinet against intervention, deploying what its members regarded as “intimidatory” tactics. The Corbyn-aligned group Momentum instructed its supporters to lobby MPs, the leader emailed them without first informing his frontbenchers and Len McCluskey, the Unite general secretary, warned that those challenging Corbyn were “writing their own political obituaries”. It was only when Watson assured Corbyn that a whipped vote would result in mass resignations that he resolved to suspend collective responsibility.

In the Labour leader’s defence, senior aides cited the opposition of a majority of members and MPs to air strikes and the mandate he achieved for an anti-interventionist foreign policy. But other allies ask why he did not therefore enforce his position. “If the cabinet and the leader disagree, it’s for the leader to say, ‘OK, thank you very much and goodbye. I will be picking a new cabinet,’” a shadow minister told me. “Ultimately, the leader whips and anybody that says differently is talking out of their arse.” By antagonising shadow cabinet ministers while dismaying some supporters, the MP concluded that Corbyn had been left with “the worst of both worlds”.

The unrest reflects the contradictory forces in the Labour leader’s project. After Corbyn appointed his shadow cabinet, Diane Abbott, who argued for the party to be whipped against air strikes, complained to MPs that too few of his supporters had been included. Just three (Abbott, McDonnell and Jon Trickett) voted for him. But this outcome was all but unavoidable. Of the 15 MPs known to have supported Corbyn, seven were newly elected, while veterans such as Dennis Skinner, Kelvin Hopkins and Ronnie Campbell had no desire to join the front bench. The result was a shadow cabinet that the Labour leader would inevitably struggle to unite on foreign and defence policy, the issues that most divide him from MPs. But Corbyn was able to state that he had fulfilled his promise to form a “unifying” and “inclusive” team.

Yet MPs contend that other appointments, over which he had a freer hand, betray a narrow and divisive strategy. Corbyn recruited unashamedly left-wing advisers, such as the Guardian columnist Seumas Milne and the economist Andrew Fisher, and made the unilateralist Ken Livingstone the co-chair of Labour’s defence review (without the knowledge of the pro-Trident shadow defence secretary, Maria Eagle). When the parliamentary party gathered on 1 December, Margaret Beckett, the former foreign secretary, declared: “We cannot unite the party if the leader’s office is determined to divide us.” To loud applause, the shadow policing minister, Jack Dromey, and Angela Smith MP called for Livingstone to be removed from the defence review. “I’m not terribly worried, actually. I’ve had a lifetime of lies and smears from the media,” Livingstone told me in response.

It is the disparity between Corbyn’s left-leaning inner circle and his centrist shadow cabinet that explains why he considered whipping the party against air strikes. The Labour leader was not even able to achieve the consolation prize of declaring that party policy was opposed to military action as the frontbenchers Andy Burnham, John Healey, Michael Dugher and Vernon Coaker vowed that they “would not leave the room” until he conceded.

Any hope that this settlement would ease relations ended quickly. Corbyn warned in interviews that there was “no hiding place” for MPs who backed air strikes, a remark that one shadow cabinet minister told me “only further exposes the leadership in their determination to undermine, intimidate and bully good colleagues”. After the Labour leader told Benn that “our bombs” would “kill people in their homes”, a spokesman for the shadow foreign secretary replied: “Inaction has a cost in lives, too.” Benn, who even opponents of air strikes say has been “enhanced” by recent events, is increasingly spoken of as a potential replacement for Corbyn. But one MP in regular contact with him told me: “I don’t think Hilary’s interested in being the leader - even in the interim.”

The Syria imbroglio has clarified the choice before Corbyn. The Labour leader can pursue co-operation, pre-emptively conceding free votes on other divisive issues such as the renewal of Trident and respecting differences of opinion. Or he can pursue confrontation, using members’ ballots to try to change party policy, appointing a more robustly left-wing shadow cabinet (described by one MP as “inevitable”) and, some argue, tolerating or even endorsing attempts to deselect critical MPs. Corbyn could, alternatively, continue to plot a course between these two paths. But as his retreat over Labour’s position on air strikes on Isis in Syria showed, he does so at the risk of pleasing none and alienating all.

Now listen to George Eaton discuss the vote on air strikes with Caroline Crampton and Stephen Bush on this week's New Statesman podcast...