The way Britain was led into war with Iraq 10 years ago was "wholly irresponsible" and the lack of intelligence on the country a national disgrace, senior military figures have told the Guardian.

Though they direct their fire principally at the Bush administration, they make clear the Blair government must share a lot of the blame.

"It was absolutely irresponsible to go in without thinking of the consequences", said Lord Guthrie, former chief of defence staff and head of the army. He added: "War is dangerous, difficult, and dirty, but usually cheaper and shorter and easier than what can happen after the fighting stops."

Donald Rumsfeld, US defence secretary at the time, had a "lot to answer for", Guthrie added, referring to the way Rumsfeld, notorious for his "stuff happens" description of widespread looting in Baghdad, allowed Paul Bremer, the US chief administrator – in effect the US governor of Iraq after the invasion – to ban the Ba'ath party and dismantle the Iraqi army.

They should have got rid of the top people but "clasped the army to their bosom", and say to them: 'Help us rebuild Iraq'", Guthrie told the Guardian.

"Why did Bremer squash any sense of the Iraqi people taking any role in their own destiny?" asked Air Chief Marshal Sir Brian Burridge, commander of British forces in Iraq at the time of the invasion. "That defies logic."

General Sir Mike Jackson, head of the army at the time, described Rumsfeld and Bremer as "intellectually bankrupt". With other British defence chiefs, he expected and wanted Iraqi military units, including Saddam Hussein's Republican Guard, to remain in place and help maintain law and order in Iraq after the invasion.

Lord Boyce, then chief of the defence staff, said he has decided to hold his fire until the Chilcot inquiry has reported (possibly by the end of the year). He questioned the legality of the war until he got an eve-of-invasion note from the attorney general's office telling him that Blair's "unequivocal" view was an attack on Iraq would be lawful.

Boyce gave a taste of what he thought about Washington's approach in his evidence to Chilcot. "I could not get across to the US the fact that the coalition would not be seen as a liberation force and that flowers would be stuck at the end of rifles and that they would be welcomed and it would all be lovely," he said.

Boyce's relations with Geoff Hoon, the defence secretary, were poor. Tensions between Hoon and all his top military advisers were heightened by Blair's concern not to alert parliament and the public that he was preparing for war. This prevented frustrated and angry defence chiefs from getting UK forces ready for the invasion until very late in the day.

Lord Dannatt, Jackson's successor as head of the army who held a senior staff post in the Ministry of Defence during the invasion, told the Guardian: "The real failure was the failure to plan properly for what happened. Whose fault was that? More, I suggest, the Americans' than ours."

He added: "Into the power vacuum created, al-Qaida and others moved and sowed the seeds of the disastrous next few years."

Bremer made things worse by "totally disbanding the Iraqi army and the Ba'ath party, the two instruments of the Iraqi state that could have exercised some control," said Dannatt.

Guthrie, Burridge, Jackson, and Dannatt, drive home the message. As Burridge put it: "One enormous vacuum developed. If you allow vacuums to develop, experience elsewhere taught us that organised crime takes over. In Iraq, it was sectarianism."

Burridge, a former pilot, pointed not so much to the distorted picture presented by the Blair government's discredited Iraqi weapons dossier, but to the failure to gather any useful information, after more than a decade, ever since the first Gulf war in 1990-91, overflying Iraq at will.

Burridge told the Guardian: "It was a national disgrace that, having flown over much of the country for 13 years, you could have not done better in building up a proper intelligence picture."

Guthrie described the first Gulf war as unfinished business, saying that Saddam Hussein should not have been allowed to get away with what he did afterwards.

The picture of Iraq 10 years ago painted by military chiefs at the time is of a dictator who needed to be, and would at some point have been toppled from power. In that sense, they say the question of "regime change" – an unlawful reason to go to war, Blair was told – was not the key issue.

The question posed by the most senior officials, including Lady Manningham-Buller, then head of MI5, as well as defence chiefs at the time, was: why now? Terrorism, not Saddam Hussein, was the big threat to Britain and British interests, they stressed.

"While I was privy to more intelligence information than most, I found what I read pretty uncompelling," Dannatt told the Guardian. But, he added: "People had to trust the judgment and integrity of the then prime minister."

What drove Blair? Burridge had little doubt: "Solidarity with the US was deeply embedded in his psyche," he said.

Blair appeared anyway to have had an appetite for military intervention, those who saw him most made clear.

In his evidence to Chilcot, Lord Wilson, the former cabinet secretary, recalled saying about Blair in March 2002, a year before the invasion: "There is a gleam in his eye that worries me."

Wilson joined other Whitehall officials and defence chiefs in saying that the cabinet was kept in the dark until it was too late to object.