It has been seven years since the end of the second siege of Fallujah – the US assault that left the city in ruins, killed thousands of civilians, and displaced hundreds of thousands more; the assault that poisoned a generation, plaguing the people who live there with cancers and their children with birth defects.

It has been seven years and the lies that justified the assault still perpetuate false beliefs about what we did.

The US veterans who fought there still do not understand who they fought against, or what they were fighting for.

I know, because I am one of those American veterans. In the eyes of many of the people I "served" with, the people of Fallujah remain dehumanised and their resistance fighters are still believed to be terrorists. But unlike most of my counterparts, I understand that I was the aggressor, and that the resistance fighters in Fallujah were defending their city.

It is also the seventh anniversary of the deaths of two close friends of mine, Travis Desiato and Bradley Faircloth, who were killed in the siege. Their deaths were not heroic or glorious. Their deaths were tragic, but not unjust.

How can I begrudge the resistance in Fallujah for killing my friends, when I know that I would have done the same thing if I were in their place? How can I blame them when we were the aggressors?

It could have been me instead of Travis or Brad. I carried a radio on my back that dropped the bombs that killed civilians and reduced Fallujah to rubble. If I were a Fallujan, I would have killed anyone like me. I would have had no choice. The fate of my city and my family would have depended on it. I would have killed the foreign invaders.

Travis and Brad are both victims and perpetrators. They were killed and they killed others because of a political agenda in which they were just pawns. They were the iron fist of American empire, and an expendable loss in the eyes of their leaders.

I do not see any contradiction in feeling sympathy for the dead US Marines and soldiers and at the same time feeling sympathy for the Fallujans who fell to their guns. The contradiction lies in believing that we were liberators, when in fact we oppressed the freedoms and wishes of Fallujans. The contradiction lies in believing that we were heroes, when the definition of "hero" bares no relation to our actions in Fallujah.

What we did to Fallujah cannot be undone, and I see no point in attacking the people in my former unit. What I want to attack are the lies and false beliefs. I want to destroy the prejudices that prevented us from putting ourselves in the other's shoes and asking ourselves what we would have done if a foreign army invaded our country and laid siege to our city.

I understand the psychology that causes the aggressors to blame their victims. I understand the justifications and defence mechanisms. I understand the emotional urge to want to hate the people who killed someone dear to you. But to describe the psychology that preserves such false beliefs is not to ignore the objective moral truth that no attacker can ever justly blame their victims for defending themselves.

The same distorted morality has been used to justify attacks against the native Americans, the Vietnamese, El Salvadorans, and the Afghans. It is the same story over and over again. These people have been dehumanised, their God-given right to self-defence has been delegitimised, their resistance has been reframed as terrorism, and US soldiers have been sent to kill them.

History has preserved these lies, normalised them, and socialised them into our culture: so much so that legitimate resistance against US aggression is incomprehensible to most, and to even raise this question is seen as un-American.

History has defined the US veteran as a hero, and in doing so it has automatically defined anyone who fights against him as the bad guy. It has reversed the roles of aggressor and defender, moralised the immoral, and shaped our societies' present understanding of war.

I cannot imagine a more necessary step towards justice than to put an end to these lies, and achieve some moral clarity on this issue. I see no issue more important than to clearly understand the difference between aggression and self-defence, and to support legitimate struggles. I cannot hate, blame, begrudge, or resent Fallujans for fighting back against us. I am sincerely sorry for the role I played in the second siege of Fallujah, and I hope that some day not just Fallujans but all Iraqis will win their struggle.

• This piece originally ran on stopwar.org.uk