Who goes on these marches? Obviously the first group of people are those who are against all war; complete pacifists who would rather lose their country peacefully than fight. I am a coward but I am not a pacifist. I believe there is such a thing as a just war.
The second group would be those who felt that this war was not right. This group would have mixed motives. Some would have felt that it was too remote, didn't really concern us. Others felt that the case for it had not been proven although, as I recall, nobody argued that Saddam Hussein wasn't a bad guy. This group wanted diplomatic means pursued, a second UN resolution or, to summarise 'a little bit more.' It follows that if they had seen what they wanted they would have backed war.
My point is this. Dodgy dossiers and faked intelligence were not a reason. Some, very smart, people felt the long-game hadn't been thought through. They were right. But nobody seemed to think they were being lied to.
But for many of us, doing the best we could with newspaper coverage, parliamentary debate and TV news, the case was just about made. This was a bad guy with a finger on some sort of chemical/nuclear trigger in one of the world's permanent trouble spots.
With hindsight I was wrong. We should have delayed and let the USA do all the working they felt called to. It would have jeopardised our relationship with the US (it was Bush's US so I wouldn't have lost too much sleep over that). If we had let them take all the blame they seem to have the ability to put failure behind them much quicker than us. US educational systems tend to value action and contribution over and above accuracy. The situation in Iraq would probably have been worse today. I value the ability of our troops on the ground to do the jobs required of them effectively and for our troop leaders to have unbelievable qualities of diplomacy after the theatre is no longer a war zone.
So I was pro-war. Just about. I started to worry when Iraqi looters took stuff from the museums of 'liberated' towns. I began to realise there had not been much thought about 'what next?'
All the tabloid press is hammering Blair now. At the time opponents of the war were hammered for being 'traitors' who won't support our wonderful troops.
I respect all those who were anti-war. Try and remember what the key reason was, for you. Watch out for hindsight.