BAGHDAD, 15 June 2006 — Government forces fanned out across Baghdad yesterday, setting up checkpoints and causing huge traffic snarls on the first day of the largest security operation in Iraq’s capital since Saddam Hussein’s ouster three years ago.

Violence dipped slightly in Baghdad, with just one car bomb killing four and injuring six. Another four people died in separate shooting incidents around Iraq. Operation Forward Together, involving tens of thousands of Iraqi Army and police forces backed by US troops, began at a crucial time — one day after US President George W. Bush made a surprise visit to Baghdad to reassure Iraqis of Washington’s continued support and exactly a week after the death of Abu Musab Al-Zarqawi.

It was also the first major action by Prime Minister Nuri Al-Maliki since his new government of national unity was sworn in on May 20, and a week after he gained the consensus he needed from Iraq’s ethnic and sectarian groups to fill three key posts — defense, interior and national security.

Tackling Baghdad’s tenuous security has been the aim of several counterinsurgency operations in the past — including one launched one year ago. That operation, code named “Lightning” failed to have any impact on the bombings, shootings and killings that have become daily fare in Baghdad.

One such car bombing killed four people and wounded six in the mixed northern Baghdad district of Qahira.

Maliki pledged yesterday not to negotiate with those who had shed innocent blood, the latest in a series of tough statements he has made since American bombs last week killed Zarqawi.

But it remains to be seen whether Maliki, a veteran politician with years of experience as an opposition activist in exile, can back up his uncompromising rhetoric with action.

What he can do is count on US President Bush and the 132,000 troops American troops in Iraq.

Bush told Maliki during a quick visit to Baghdad late Tuesday that the United States stands with his government and would not withdraw troops until Iraqis were ready to take over security of their country.

“When America gives its word, it keeps its word,” Bush said.