In a year of continuity politics like 2013, the vote at the end of August on whether to back intervention in Syria, after the chemical weapons attack on a Damascus suburb, stands out. Its significance was greater than the miscalculations that preceded it suggests. What was not at all clear at the time was exactly how to understand it. The retrospective analysis that is happening now is where it will be decided and how will it be framed by two big debates. The first is about Britain and the world, the second about the British constitution.

There are two narratives. One is that Britain has lost its collective nerve and set the stage — as Aneurin Bevan once warned a Labour party conference — for the public humiliation of its leaders in the world’s negotiating chambers. From the puerile calculations of a struggling opposition at the end of the summer break, this narrative goes, stem the mortifying put-downs endured by David Cameron at the hands of the Russians and the Chinese. Britain, one pundit claimed, had been left with the international credibility of Luxembourg.

Alistair Burt, an ally of Foreign Secretary William Hague’s and a former middle east minister, has at least one foot in this camp. He told the Guardian in an interview this week that it was now clear parliament would only vote for military action to defend national territory.

The doctrine of progressive interventionism, the doctrine of the responsibility to protect was carelessly killed off in the lobbies of the House of Commons, its death confirmed by Barack Obama’s immediate decision to consult a Congress already known to be reluctant.

The second narrative is that the Syria vote was a welcome resurgence in parliamentary power. The 2010 House of Commons — already a noticeably awkward chamber, partly because of the number of new MPs in all parties with more independent views and experience and partly because there is no majority — had struck a blow against the executive that marked an important advance in its ability to make the government accountable.

Of course, parliament’s role in decisions of war and peace had been confirmed by Tony Blair at the time of the vote on Iraq. But because parliament gave him the answer he wanted, the profound constitutional implications were obscured. Now parliament has actually vetoed a government’s proposal for military intervention, its right to do so has been confirmed — another layer in the slow accretion of precedent that makes the constitution.

According to Burt, the government was so thrown by the unexpected outcome (a fact that raises serious but second-order questions about the operation of party discipline) that it was left uncertain whether it could legally offer any assistance at all to the US plan to retaliate against Bashar Al Assad’s use of chemical weapons. He may be exaggerating for effect. The case remains that the government can do anything it wants as long as it can carry it in parliament.

His more serious claim is that parliament will never vote for military intervention again. There is no reason to suppose that at all. There is no evidence that a different question in different circumstances will produce the same answer. But 12 years after 9/11, people are understandably weary of the endless demands made in its name and — informed by the evidence — more and more doubtful that sending in the military is the best way of promoting peace and security.

The really important point that underlies this debate is that the reluctance of parliament to fall in line behind another US military operation has led to the diminution of British influence abroad. This is what will be settled in the national mind by the way the argument over the vote is decided.

But the actual question is whether Britain needs to go on spending what in global terms are disproportionate amounts on defence — shortly to include the upgrading of Trident — in order to have a voice in the world.

­— Guardian News & Media Ltd