It’s hard, even in the US, to find a politician or senior military figure who now thinks the invasion of Iraq was a good idea. Most of the people in Britain who shouted for it so loudly in 2002 and 2003, like Tony Blair and Alastair Campbell, shuffle their feet and try to change the subject.
You can trace Brexit and the rise of Scottish nationalism directly back to the Iraq invasion; not to mention all the other signs that Britain has convinced itself politicians can’t be trusted. It revealed in stark terms America’s military weaknesses and the fragility of the Western alliance.
Would Putin have invaded Ukraine if it hadn’t happened? Probably not. And China under Xi Jinping might well not have thought of crushing Hong Kong or invading Taiwan. Twenty years later, the two big questions still hang in the air: why did George W Bush do it, and why did Tony Blair back him? They’re actually easy enough to answer.
September 11 was such a shock to America’s self-confidence that Mr Bush’s neo-con backers felt they had to stage a major demonstration of American power; while Tony Blair believed that Britain had to be America’s most loyal lieutenant. Mr Bush’s people knew that Saddam Hussein looked strong and tough, yet was actually a pushover. General David Petraeus, who was later given the job of rescuing the US from the disaster, knew all along that the invasion was a terrible idea. So did the Secretary of State, Colin Powell, though he was too weak (his own word) to resist it. Half the population of Britain, according to the opinion polls, agreed.
A lot of the invasion’s supporters thought it would be retrospectively self-justifying: they assumed that Saddam Hussein had plenty of weapons of mass destruction, which would be uncovered by the invading forces. After all, he’d used poison gas against Iran and against his own Kurdish people in Halabjeh, and threatened long and loudly to use nuclear weapons against the invaders. There were none: he smuggled his WMDs to Syria before the war began.
Adnan Pachachi, a dissident who became vice-president after the invasion, told me he knew it was going to be a disaster, and went to Washington to beg George W Bush not to go ahead with it. To his horror, he found that neither Mr Bush nor any of his close advisers realised that Iraq’s Muslims were divided into Sunnis and Shias – the fault-line that led to the appalling civil war. The British were better informed, but because Tony Blair was so determined to follow wherever Mr Bush led, no one wanted to point out the problems, either at home or in meetings in Washington. ‘They just thought I was gutless when I talked about the downside,’ a British general said afterwards.
And so the horror began. Hundreds of thousands of Iraqis died in the civil war which followed the invasion. The US military machine wasn’t up to the job, and individual soldiers sometimes turned viciously on the civilian population when they were attacked: something I saw with my own eyes over the months and years that followed March 2003.
I spent altogether more than a year of my life in Iraq during that period, and look back on much of it with revulsion. I lost seven friends, and still suffer from the injuries I received. As for the US, it spent a total of $2.4trn (£1.97trn) on the war: enough, according to Oxfam, to eliminate world hunger for 60 years. And the essential outcome? It demonstrated for all to see that the West was no longer the power it had once been.
John Simpson is the BBC’s world affairs editor. His programme, Unspoken World, returns to BBC Two in May.