As thousands more US soldiers began deploying in the Gulf for what could be a campaign lasting months, there were growing questions in London and Washington over the failure to anticipate the stubborn resistance being encountered.

At the start of the war British military officers were confident that the southern city of Basra would fall quickly, that the Shia Muslims in the south would rise up against Saddam and that there would be token resistance on the road to Baghdad. “The intelligence assessment seriously underestimated what to expect,” one Whitehall source, who briefed Downing Street on the dangers before the war, said.

His advice was largely ignored, even though Saddam was openly making careful preparations to defend himself. He armed and trained irregular forces, bribed tribal leaders and used propaganda to portray the looming war as an attempt by America to conquer the country and steal its oil.

It is understood that British intelligence had been receiving reports from inside Iraq. It strongly suggested that the regime was weak and would topple if pushed, particularly in the southern city of Basra, which is the area allocated to the British forces.

Part of that assessment was based on the uprisings of 1991, when thousands of Shias rebelled against Saddam and were brutally suppressed by his forces.

British government sources admitted yesterday that there had been a “general expectation” on both sides of the Atlantic that “the Iraqi people would revolt against Saddam as they had in 1991” or at least that there might be coup “within the higher echelons” of the regime.

One foreign intelligence source, with good first-hand knowledge of Iraq, said that this analysis was flawed. He insisted that the Shias may hate Saddam, but that they have no love for the Americans and British, who let them down 12 years ago and whose motives today are greeted with suspicion.

“The Shias of the south fought hard against Iran for eight years during the Iran-Iraq War. They were Iraqis first and Shias second. There is a strong nationalist feeling in Iraq and Saddam is an expert at exploiting it,” he said.

Much of the blame in London was directed at Washington. Most of the shared US-British intelligence is said to have been about troop movements and whether Saddam possesses weapons of mass destruction. There are now doubts about the veracity of at least some of this information.

“Plans have been driven by US intelligence,” a Whitehall source said. “But we have been aware for some time that they rely, perhaps too much, on radio intercepts and satellite photography.”

The Foreign Office is believed to have been concerned at the credence attached in Washington to information from Iraqi exiles with political connections to the Bush Administration. They widely predicted that the Iraqi Armed Forces would defect as soon as the war broke out.

Criticism is also growing within Washington against hawks in the Bush Administration. They were supremely confident that America’s overwhelming military might and its tactic of “shock and awe” would cause the Iraqi military to buckle and leave the regime’s hierarchy isolated. Toby Dodge, an expert on Iraq at Warwick University, said that much of this assessment had been based on wishful thinking by the neo-conservatives, who lacked first-hand experience of modern Iraqi society and politics.

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