TENS of thousands of Iraqi troops will flood on to the streets of Baghdad this morning in the biggest operation yet to regain control of the city.

The move comes after George Bush’s surprise visit to the Iraqi capital to build on the momentum created by the formation of a new Iraqi Government and the death of the terrorist leader Abu Musab al-Zarqawi.

Mr Bush’s visit marked the beginning of a new Iraq strategy designed to pave the way for an American military withdrawal.

“The future of the country is in your hands,” Mr Bush told the stunned Iraqi Cabinet, who had assembled at the US Embassy in Baghdad’s green zone expecting to participate in a teleconference with the President and his war Cabinet at his mountain retreat at Camp David.

Instead, Mr Bush had flown in on a visit so cloaked in secrecy that even Nouri al-Maliki, the Iraqi Prime Minister, did not know of it until he clapped eyes on the President in the hall of Saddam Hussein’s former palace.

The image of the two leaders standing shoulder to shoulder was clearly designed to suggest a handover of responsibility for security to the new Iraqi Government amid growing pressure in America for a clear exit strategy from the increasingly unpopular conflict.

The talk during the visit was not of winning war but of how America could help Iraq to chart its future course.

“The decisions you and your Cabinet make will determine as to whether your country succeeds, can govern itself, can sustain itself and defend itself,” Mr Bush told Mr al-Maliki at a press conference. “And so I’ve come not only to look you in the eye, but also to tell you that when America gives its word, it will keep its word. It’s in our interest that Iraq succeeds.”

The new strategy, described by one US official as the “last, best chance to get this right” after three years of escalating violence, begins this morning with the Baghdad crackdown.

More than 70,000 predominantly Iraqi troops will hit the streets to hunt down and storm insurgent hideouts, calling in airstrikes if required.

The city is to be divided into zones on the lines of a British model used in Northern Ireland, with US commanders heading up a mixed force of coalition and Iraqi troops, backed by tanks and armoured vehicles, to purge each sector of known insurgent cells.

The Iraqi troops will wear a new uniform aimed at thwarting the insurgent tactic of operating in the guise of different security forces, from commandos to policemen. Personal weapons will be banned and a curfew between 9pm and 6am imposed on the city in what promises to be the biggest crackdown since American forces took Baghdad in April 2003.

“The raids will be very tough,” Mr al-Maliki said. “There will be no mercy towards those who show no mercy to our people.”

Another priority is the dismantling of the Shia militias that have hijacked the state security forces and have been carrying out their own revenge killings against the Sunni minority.

While the demise of the al-Qaeda leader al-Zarqawi may slow the spate of kidnappings and beheadings, his greatest success — fomenting a civil war between Sunnis and Shias — has acquired a momentum of its own that will be hard to stop.

The new Iraq strategy will also include the influx of billions of extra US dollars for the reconstruction of sewerage systems and electricity supplies across the country, especially in Baghdad, to win back the support of ordinary Iraqis disaffected by the lack of progress.

Mr al-Maliki was to present the Baghdad crackdown as an Iraqi government operation, highlighting the shift of responsibility away from the Americans.

But a senior US military official in Baghdad told The Times that the security plan was the work of the Americans. He said that the document was drawn up after Mr al-Maliki appealed to General George Casey, the top US commander in Iraq, for a plan to turn the insurgency around.

Mr Bush’s cloak-and-dagger arrival in Baghdad underlined how far the Iraqis have to go in securing their war-ravaged capital — and, indeed, exercising full sovereignty.

Minutes before his meeting he had flown into Baghdad international airport, which was shut down and controlled by US forces without the knowledge of the Iraqi Government, whose leader was not trusted with advance notice of his special visitor.

Elsewhere in Iraq yesterday the bombing continued despite al-Zarqawi’s death, with fifteen killed in six attacks in the northern city of Kirkuk.

In a statement issued on an Islamic website, Abu Hamza al-Muhajir, the new leader of al-Qaeda in Iraq, vowed to avenge al-Zarqawi’s death. “The day of vengeance is near and your strong towers in the green zone will not protect you,” he said, before warning Iraqis who co-operated with US forces: “You will see what we have in store for you because of your betrayal and apostasy. Our swords are poised above your necks.”

A NEW STRATEGY

Hundreds of thousands of new Iraqi troops to be trained to take the place of Americans

Times Recommends

• No apology for Germany’s own Nazi victims
• Intricate web of fear and hope tying down deal
• Victims remembered a year after Mumbai attacks