Patrick Cockburn: Deaths are a huge blow to al-Qa'ida – but will not stop bombs

The deaths of the two leaders of al-Qa'ida in Iraq is a serious blow to the organisation, which has been greatly weakened since it was at the height of its power from 2005 to early 2007. But their killing will not stop the bombs in Baghdad. Such attacks are very difficult to prevent so long as there are suicide bombers willing to drive vehicles packed with explosives which detonate where they will cause maximum civilian casualties. Abu Omar al-Baghdadi was always a shadowy figure; indeed, some argued he did not really exist. He mainly achieved notice because of repeated claims by the Iraqi government that it had killed him. Abu Ayyub al-Masri was also an indistinct figure, and neither man achieved the notoriety of Abu Musab al-Zarqawi, the founder of al-Qa'ida in Iraq, who was killed in a US airstrike in 2006.

Al-Qa'ida in Iraq never had much connection with Osama bin Laden's group. Zarqawi had little to do with him when both men were in Afghanistan. But from 2003 the Iraqi group, well-financed from abroad, expanded rapidly – although its attacks were primarily aimed at Shia civilians. By 2006, it had taken over large areas where Sunni Arabs were the majority and tried to dominate the whole resistance movement by setting up the Islamic State of Iraq as an umbrella group for all insurgents. It was also demanding that each Sunni family send a son to its ranks.

By grossly overplaying its hand within the Sunni community and provoking a ferocious Shia counter-reaction, al-Qa'ida set the stage for a split in the resistance. Much of it laid down its arms, formed the al-Sahwa movement and allied itself to the Americans. Al-Qa'ida reorganised itself into cells, less easily penetrated by the Iraqi security forces, and continued its war against Shia targets but almost never attacked US troops. The death of its leaders may provoke another onslaught by remaining al-Qa'ida cells to prove they are still in business.