Even though I spent three years writing a book on the 15 February 2003 anti-war march in London and the wider anti-Iraq war movement, I've come to realise I myself radically underestimated the significance of the day.
Arguably 15 February 2003 is one of the most important dates in recent British history, especially in terms of how people see politicians and their ability to influence government policy. Campaigning journalist Owen Jones explains that when he speaks in schools he is often asked by pupils how they can change anything if two million demonstrators on 15 February 2003 couldn't: "Forget the expenses scandal. It was Iraq that exploded what trust millions had in our political establishment." What happens when large numbers of people become disillusioned by peaceful protest marches was highlighted by Laurie Penny on the 10th anniversary of the march: "When 4,000 students and schoolchildren smashed up the entrance to the Conservative Party headquarters and held an impromptu rave in the lobby, several young people mentioned the Stop the War march of 2003, how all that passive, peaceful shuffling from one rally point to another had failed to achieve anything concrete."
However, contrary to most people's understanding of the Iraq War, there is considerable evidence the anti-war movement actually came very close to stopping British involvement in the invasion of Iraq and toppling the government. The key date was 11 March 2003, just over a week before the invasion. According to the Sunday Telegraph, on this day the Ministry of Defence "was frantically preparing contingency plans to 'disconnect' British troops entirely from the military invasion of Iraq, demoting their role to subsequent phases of the campaign and peacekeeping." A Sunday Mirror report explained that the crisis had been triggered by a phone call between then defence secretary Geoff Hoon and his US counterpart Donald Rumsfeld where Hoon "stressed the political problems the government was having with both MPs and the public."
While this near success is important to highlight, last year produced the anti-war movement's biggest victory - stopping the US-UK attack on Syria in August 2013. With the Coalition Government's motion for military action defeated by 13 votes, almost all of the news coverage noted the "spectre" of the Iraq War hung over the House of Commons. During Ed Miliband's much-discussed face-to-face meeting with David Cameron and Nick Clegg in Downing Street just before the vote, "Ed said to the Prime Minister: 'You have to realise that after Iraq nobody trusts any of us'."
The political elite has every interest in minimising and dismissing popular protest but it was the anti-war movement that played the crucial role in highlighting government deceit in the run-up to the invasion of Iraq and mobilising and educating so many people.
Across the Atlantic, Obama was poised to attack Syria but "the lack of a British blessing removed another layer of legitimacy", according to the New York Times. At this point the president took the unusual step of seeking congressional approval for military action, telling senior aides one of the reasons for his decision was "a sense of isolation after the terrible setback in the British Parliament." Former Vice Chief of Staff of the US Army Jack Keane confirmed this version of events, noting David Cameron's defeat instilled "palpable fear" in Obama.
With the US anti-war movement applying pressure on their representatives in Congress the outcome of the votes in the Senate and House of Representatives was far from clear. With the political storm about to come to a head, the Russian proposal to destroy Syria's chemical weapons was, after initially being dismissed, eventually welcomed by the US Government. Fast forward to today and though there is a delay, the destruction of Syria's chemical weapons continues and a US-led attack on Syria has been averted.
Paraphrasing former UK Foreign Secretary Malcolm Rifkind, a supporter of an attack on Syria, last month the Guardian explained "the Commons vote had strengthened diplomacy in the Middle East". Rifkind elaborated: "In the last three or four months we have had, in a way no one predicted, not one but two diplomatic breakthroughs: the Syrian chemical weapons agreement and the interim deal in Iran."
While many factors are involved in such momentous shifts in world diplomacy, it is clear that a direct line can be drawn from the massive anti-Iraq war protests in 2002-3 to the UK government being forced to back down from military action against Syria ten years later. This in turn played an important role in delaying the US march to war, which opened up space for diplomacy - on Syrian chemical weapons and the Iranian nuclear programme.
Although it didn't stop the war in 2003, the influence of the UK anti-Iraq War movement has stretched very far indeed and likely saved tens of thousands of lives in the Middle East.