LONDON – Britain’s decision to go to war in Iraq was a failure born of flawed intelligence, lack of foresight and “wholly inadequate” planning, an official inquiry concluded Wednesday in a report seven years in the making.

Retired civil servant John Chilcot, who oversaw the inquiry, said “the U.K. chose to join the invasion of Iraq before the peaceful options for disarmament had been exhausted. Military action at that time was not a last resort.”

The 2.6-million-word report is an exhaustive verdict on a divisive conflict that – by the time British combat forces left in 2009 – had killed 179 British troops, almost 4,500 American personnel and more than 100,000 Iraqis.

It continues to divide Britain and overshadows the legacy of then-Prime Minister Tony Blair. As Chilcot introduced his report at a London conference center on Wednesday, dozens of anti-war protesters with placards reading “Bliar” rallied outside.

For families of British troops who died in the conflict, the long litany of mistakes by Blair and others provides some vindication of their struggle to hold the war’s planners to account.

But it did not declare the conflict illegal, which might have opened the way for Blair to be prosecuted for war crimes.

Chilcot refrained from saying whether the 2003 invasion was legal and didn’t accuse Blair of deliberately misleading the public or Parliament. But he said that “the circumstances in which it was decided that there was a legal basis for U.K. military action were far from satisfactory.”

For Iraqis, it was little comfort. They continue to live with violence, including a massive weekend bombing in Baghdad claimed by the Islamic State group that killed more than 175 people.

“Since 2003 until now, our country has been a scene of destruction, killing, massacres, explosions and sectarianism,” Baghdad resident Ali al-Saraji said.

He said that Blair “destroyed our country” and should be prosecuted as a war criminal.

An emotional Blair told a news conference that going to war in Iraq was “the hardest, most momentous, most agonizing decision I took in my 10 years as British prime minister.”

He said that “I express more sorrow, regret and apology than you may ever know, or can believe,” for all the things that went wrong. But, he added: “I took this decision because I believed that it was the right thing to do.”

Chilcot said “the people of Iraq have suffered greatly” because of a military intervention “which went badly wrong.”

The report said Blair’s government presented an assessment of the threat posed by Saddam Hussein’s weapons with “certainty that was not justified.” The inquiry also found military planning for the war and its aftermath were not up to the task.

Relatives of soldiers killed in the conflict said they hadn’t ruled out legal action.

“All options are open,” said Matthew Jury, a lawyer for some of the families.

In a statement, a group of families said “we must use this report to make sure all parts of the Iraq fiasco are never repeated again.”

“Never again must so many mistakes be allowed to sacrifice British lives and lead to the destruction of a country for no positive end,” they said.

The inquiry was set up after U.K. combat troops left Iraq in 2009 by then-Prime Minister Gordon Brown, who was under pressure for a public accounting of the deeply unpopular conflict.

Chilcot and his panel heard from 150 witnesses and analyzed 150,000 documents. His conclusions are a blow to Blair, who told President George W. Bush eight months before the March 2003 invasion – without consulting government colleagues – “I will be with you whatever.”

The report says Blair went to war to stand shoulder-to-shoulder with Britain’s main ally, only to find the U.K. excluded from most important decision-making about the military campaign and its aftermath.

“Mr. Blair, who recognized the significance of the post-conflict phase, did not press President Bush for definite assurances about U.S. plans,” the report concluded.

And it said that after the invasion, Britain had only “limited” ability to influence U.S. decision-making.

Iraq descended into sectarian strife after the occupiers dismantled Saddam ‘s government and military apparatus, unleashing chaos that helped give rise to the Islamic State group.

Jack Straw, Britain’s foreign secretary at the time, blamed the U.S. for that, saying actions by U.S. administration officials “blindsided” the British government.

The report found failings by military chiefs who did not provide adequate equipment to forces in the field, and whose main post-invasion strategy “was to reduce the level of (U.K.) deployed forces.”

The report concludes that Britain’s combat mission, which ended in 2009, did not achieve the objectives laid out in 2003 and saw British forces make a “humiliating” deal with militias in southern Iraq to avoid attacks.

“The U.K. failed to plan or prepare for the major reconstruction program required in Iraq,” the report said.

The war has overshadowed the legacy of Blair, whose government has been accused of exaggerating intelligence about Saddam’s alleged weapons of mass destruction in order to build support for the invasion.

Chilcot criticized spy chiefs who failed to ensure their partial intelligence about Saddam’s weapons was not hardened into certainty by government spin. He said they also failed to consider “that Iraq might no longer have chemical biological or nuclear weapons” – which turned out to be the case.

The report said the widespread perception that the government had exaggerated intelligence evidence “has produced a damaging legacy, including undermining trust and confidence in government statements.”

The report also faults Blair for making key decisions with only a few key aides rather than through collective Cabinet consultation.

Chilcot’s report has been repeatedly delayed, in part by wrangling over the inclusion of classified material, including conversations between Blair and Bush. Some of Blair’s pre-war letters to the president are published in Chilcot’s report, but not Bush’s replies.

It remains unclear what, if any, legal action could be taken against Blair or others.

The International Criminal Court is looking into alleged war crimes by British troops in Iraq, but says has said that Britain’s decision to go to war falls outside its jurisdiction.

Sarah O’Connor, whose airman brother died in a plane crash in Iraq in 2005, said the war remained “an indelible stain on the whole world.”

“There is one terrorist in the world that the world needs to be aware of, and his name is Tony Blair,” she said.