For all its intensive diplomatic activity, the international community has been powerless to prevent the escalating horrors of the Syrian civil war.
It has not been for want of trying, with numerous attempts to negotiate ceasefires, open dialogue and impose sanctions on President Bashar al-Assad having little impact on the bloody impasse.
For the moment Syria has slipped down the agenda of Western leaders whose efforts are focused on defusing the crisis provoked by the deployment of Russian troops onto Ukrainian soil.
As the initial protests in the southern city of Deraa in 2011 spiralled into civil war, and evidence of human-rights atrocities mounted, Britain, the European Union and the US called for Assad to step down and imposed sanctions on the nation’s ruling elite.
A six-point peace plan for Syria, drawn up by the former UN Secretary-General Kofi Annan and backed by the Arab League, was launched a year after the war began, but foundered within two months as the violence intensified. A similar initiative by the UN envoy Lakhdar Brahimi also failed.
The biggest stumbling block to concerted international pressure on Damascus has always been Russia, which has enjoyed a close relationship with the Assad regime, and refused (along with China) to join UN Security Council resolutions condemning Damascus.
The process of bringing all the participants around the negotiating table – based on setting up a transitional government in Syria – began last May with two rounds of talks taking place with little progress in Geneva this year.
The hunt for a lasting settlement – potentially using military firepower – was given new impetus by the release of footage of a chemical weapons attack on a Damascus suburb, with world leaders warning a “red line” had been crossed. By the end of August, it seemed that US-led strikes on Syria could happen within days.
By now David Cameron had taken from William Hague, the Foreign Secretary, responsibility for leading the British response to the Syrian crisis.
He struck a notably hawkish stance, calling MPs back from their summer break last year to vote on a Commons motion that left open the possibility of “military action that is legal, proportionate and focused on saving lives by preventing and deterring further use of Syria’s chemical weapons”.
Mr Cameron suffered the most humiliating moment of his premiership when the motion was defeated after Tory MPs queued up to condemn a rush for war and raise fears that intervention could inadvertently hand power to jihadists operating in Syria.
It was the first time a Prime Minister’s foreign policy had been defeated in a parliamentary vote since the 18th century.
It also marked a turning point in the world’s response to the tragedy in Syria as President Barack Obama backed off from intervention.