The attack inside the Iraqi parliament building yesterday was symbolic as well as sadistic. It was a calculated insult as well as an assault on an institution that physically displays how Iraq has changed since the fall of Saddam Hussein. It was obviously designed to kill more parliamentarians, timed as it was to strike the canteen during lunchtime between sessions. It was also planned to demonstrate that even the green zone, the highly fortified centre of Baghdad, cannot be made entirely safe from the terrorists.

A similar symbolism applied to the truck bombing of the Sarafiya bridge, which is one of the main arteries linking the west and east of the capital city. The amount of explosives employed was so huge that it should have destroyed the bridge outright and killed many more than those who were unfortunate enough to be caught on it. Although badly damaged, this structure (originally built by the British nine decades ago) was not destroyed. That such a strategically important site could be targeted only hours before the national parliament was hit will, nevertheless, be taken by some as proof that the US/Iraqi “surge” in Baghdad and elsewhere is a failure.

The facts on the ground contradict such an assertion. The surge is misnamed and misunderstood in several respects. The name offers the impression of a huge increase in US troop levels when the rise is modest and will not, in any case, be completed for another two months. The Iraqi Army has actually provided much of the new muscle that has been witnessed in Baghdad. This is less a case of intensified combat than a more sophisticated and concentrated series of measures. These consist of extra checkpoints, patrols, curfews and an effort to acquire better intelligence so that both the Sunni extremists who are associated with al-Qaeda and Shia death squads can be contained.

To the surprise of many sceptical observers, there is real evidence of tangible progress. The numbers of recorded attacks in Baghdad halved between December and last month, while the tally of reported murders has fallen just as sharply. They remain far too high but no longer look as if they might spiral out of control. The military and political effort to divide foreign Sunni militants with overt al-Qaeda sympathies from the main-stream Sunni Iraqi nationalists has been working in Baghdad itself and also, crucially, in the vast Anbar province, where tribal leaders have been actively cooperating with the US Army for the first time since the initial invasion in 2003.

The Shia extremists often described as followers of Moqtada al-Sadr have also been disrupted. Internal disputes have obliged some to lie low in Baghdad, others to shift elsewhere in Iraq and another band to bolt for Iran. Al-Sadr himself, once the kingmaker of the current Iraqi Government, has been forced into hiding. His supporters are still capable of appalling atrocities but, again, the attempt to drive a wedge between conventional Shias and the violent fringe has had rewards.

All of which makes the case, as Senator John McCain argued earlier this week, for this strategy to be continued at least through the end of this year. A more credible and effective security strategy cannot, though, be an end in itself. It is for the Iraqi Government to seize this chance to finalise a comprehensive economic and political settlement that all or most of Iraq’s communities deem acceptable. If any good is to come of yesterday’s bombings, it will be to impress on ministers the urgent need to reach such a bargain.