It was inevitable that brutal attacks would follow the Iraqi elections, but the atrocity in al-Hillah yesterday was a sign of the ruthlessness of insurgents seeking to undermine the gradual progress being made in the country. The victims were, as usual, innocent Iraqis, awaiting medical checks to allow them to take government jobs. They were targeted not only because the terrorists are trying to intimidate anyone ready to work for the Iraqi State, but, more cynically, because they were mostly Shia. There could not have been clearer proof to Iraqis, their Arab neighbours and the wider Muslim world that the aim of the fanatics setting off suicide bombs is not to drive out foreign troops but to engulf Iraq in bloody sectarian war.

Their desperation has been strengthened by the elections. These showed that the vast majority of Iraqis, including many moderate Sunnis, embraced the chance to elect their own government and have not been intimidated by the threats of al-Qaeda and Saddam loyalists. The vote also showed how hollow are the claims that the “resistance”, as the terrorists style their killings, is in some way connected to Iraq’s freedom. It is not. The strategy is the classic bloody logic of all insurgents: target the innocent in order to provoke anger, despair and retaliation, and then use that retaliation to rally all Sunnis behind the terrorists purporting to defend their community against a vengeful Shia majority.

To their enormous credit, Shia Iraqis and their leadership have refused to be provoked. As well as the al-Hillah bomb, suicide bombers killed at least a hundred others over the two-day religious commemoration that began ten days ago. Religious leaders have been attacked, mosques bombed and the Shia faith denounced. And still the leadership has counselled caution, called on Sunnis to join the new Government and held in check any vigilantes vowing vengeance. Such restraint has been intensely frustrating for the terrorists.

The Shia leadership well understands the importance of winning the propaganda war, however. Syria’s handing-over of Saddam’s half-brother is of crucial importance. Not only was this detested former intelligence thug actively organising the terrorist campaign in Iraq, he was doing so with the connivance of the Syrian Government — which only days earlier insisted that it knew nothing of Saddam loyalists sheltering in Syria.

Damascus may think that its volte-face, which included rounding up 29 other Baath fugitives, may end the international pressure on the embattled Assad regime. Its miscalculation is as obvious here as in Lebanon and Israel, where it stands accused of masterminding the Tel Aviv bombing. The reluctant new co-operation with Iraq only underlines the extent to which Syria has been complicit in Iraqi terrorism until now. It underlines the logic behind the warnings in Washington and Baghdad about its intentions. Isolating the Sunni extremists will be a long, hard job. But Shia forbearance and pressure on Damascus are crucial in building a secure and free Iraq.