By Kathryn Westcott
BBC News Online
The population of Basra consists largely of Shia Arab Muslims, most of whom have little affection for Saddam Hussein and his Sunni Arab ruling elite.
The city still bears the scars of the brutal suppression by Saddam Hussein's special forces of a Shia rebellion at the end of the Gulf War. Tens of thousands of Shia across the southern region were killed, tortured or imprisoned. Many others fled to Iran.
One objective for the coalition troops is to ensure that the fractious Shia south does not erupt into civil war.
A large number of fighters from the military wing of the main Shia opposition party are based in Iran, and there are fears that they may cross the border and initiate a scramble for power.
When a raid into the city finally began on Sunday after days of laying the siege, British commanders said their policy of "advancing slowly and softly as opposed to hitting the door from day one" had paid off and the British troops were welcomed in the streets.
But Iraqi militia - whose number is unknown - remain a constant threat.
According to reports, coalition commanders have drawn up extensive plans for humanitarian operations once Basra and the key areas in the south are secured.
With its close proximity to Iraq's borders with Kuwait and Iran and access to the Gulf, Basra has long been a key entrance point to the country. As such, it has long borne the brunt of wars.
It is Iraq's second-largest city and is both strategically and psychologically important.
Basra and the other southern Gulf port of Umm Qasr long figured highly in US war plans.
Securing Umm Qasr was a priority because it is a deep-water port and the country's main supply route by sea.
Basra is key to Iraq's southern oil wealth
Basra, itself, is at the southern end of a route to the capital 560 kilometres (350 miles) to the north-west, along the valleys of the Tigris and Euphrates rivers.
Basra and Umm Qasr are also key to Iraq's southern oil wealth on the Faw peninsula. One of the first major objectives was to seize port facilities and secure the nearby 1,000 or so oil wells, amid fears that fighters loyal to Saddam Hussein would set them alight.
Home to 'traitors'
Tradition has it that Basra was built near the biblical Garden of Eden.
But there is little evidence of paradise in this hot, swampy region.
Basra has become a shadow of its former economic self
Much of the south has not shared the material benefits provided by the once-busy port and oil fields. Few state resources have been spent on an area thought by many in the ruling Sunni Arab minority as traitorous.
Basra has for more than a decade been a shadow of its former economic self.
In ancient times it was the first major port in the Gulf, from whose shores the legendary vagabond Sinbad the Sailor embarked on his adventures.
Today hulks of ships, half sunk during the Iran-Iraq war of the 1980s, lie rusting in the Shatt al-Arab.
Towering bronze statues of Iraqi soldiers along the waterway point accusingly at Iran - a grim reminder of the role the city played in Iraq's war with its neighbour.
It became the headquarters for Iraq's armies and was subjected to heavy shelling by Iran. Tehran tried to capture Basra but never made it through the forbidding marshlands.
A few years later, it was also pounded by the allied forces during the Gulf War - buildings were shelled and flattened, and electricity and water supplies were cut off by the bombing.