What did the British achieve during their four years in Basra?

Aside from the search for weapons of mass destruction, the main goal of the coalition was to depose Saddam Hussein. This was achieved within a few weeks. For this reason British troops were welcomed initially by Basra’s majority Shia population, which had been oppressed by Saddam. But with too few troops to maintain security, the mission soon started to go wrong. Shia militias, supported by Iran, gradually took control of the streets.

Ever since, British troops have been doing little more than holding the ground they stand on. It has come at a heavy price in dead and wounded.

What impact will the withdrawal have on the city?

What little influence the British had on Basra city has now been further reduced. British forces at Basra airport could still return to the city but in reality this would be extremely difficult and dangerous, and unlikely to happen unless there is an emergency.

The power vacuum will be filled by Iran and its allies, in particular the al-Mahdi Army loyal to Moqtadr al-Sadr. The militias are now free to consolidate their positions and secure control of the city, including the hugely profitable oil-smuggling business, but there may be a turf battle.

How will Iran respond?

Iran will regard the withdrawal as a huge victory for their policy of encouraging Shia militias against American and British forces. There will be little to stop the Iranians extending their influence over the city and the province.

How will the region react?

The wider Arab world will be deeply concerned. Although the number of troops pulling out is small — only 550 — symbolically it will be viewed as a victory for Iran over a large area of Arab land. Kuwait in particular will be concerned since Basra is just across its border.

To many minds, the main battle in the Middle East is being waged by America, Israel and its Arab allies to limit Iran’s influence in the Arab world. So far, the Iranians are making all the running.

Last year Hezbollah, the Iranian-backed Shia militia in Lebanon, fought the Israeli army to a standstill in southern Lebanon. Earlier this year Hamas, the militant Palestinian group supported by Tehran, seized control of the Gaza Strip.

Now Basra has been abandoned by the British. This all coincides with a claim by President Ahmadinejad at the weekend that Iran had mastered the nuclear fuel cycle, which the West fears is a prelude to building an atomic bomb.

Although the withdrawal may be a relief to British soldiers, their relatives and the public back home, the wider Arab world will worry that Iran is on the march and that a new showdown is looming.

Times Recommends

• Times Charity Appeal: SolarAid
• Is it Black Monday all over again for Dubai?
• Behind the scenes at the biggest deal