It has quickly become clear that Iraq is not a liberated country, but an occupied country. We became familiar with that term during the second world war. We talked of German-occupied France, German-occupied Europe. And after the war we spoke of Soviet-occupied Hungary, Czechoslovakia, eastern Europe. It was the Nazis, the Soviets, who occupied countries. The United States liberated them from occupation.

Now we are the occupiers. True, we liberated Iraq from Saddam Hussein, but not from us. Just as in 1898 we liberated Cuba from Spain, but not from us. Spanish tyranny was overthrown, but the US established a military base in Cuba, as we are doing in Iraq. US corporations moved into Cuba, just as Bechtel and Halliburton and the oil corporations are moving into Iraq. The US framed and imposed, with support from local accomplices, the constitution that would govern Cuba, just as it has drawn up, with help from local political groups, a constitution for Iraq. Not a liberation. An occupation.

And it is an ugly occupation. On August 7 2003 the New York Times reported that General Sanchez in Baghdad was worried about the Iraqi reaction to occupation. Pro-US Iraqi leaders were giving him a message, as he put it: "When you take a father in front of his family and put a bag over his head and put him on the ground, you have had a significant adverse effect on his dignity and respect in the eyes of his family." (That's very perceptive.)

We know that fighting during the US offensive in November 2004 destroyed three-quarters of the town of Falluja (population 360,000), killing hundreds of its inhabitants. The objective of the operation was to cleanse the town of the terrorist bands acting as part of a "Ba'athist conspiracy".

But we should recall that on June 16 2003, barely six weeks after President Bush had claimed victory in Iraq, two reporters for the Knight Ridder newspaper group wrote this about the Falluja area: "In dozens of interviews during the past five days, most residents across the area said there was no Ba'athist or Sunni conspiracy against US soldiers, there were only people ready to fight because their relatives had been hurt or killed, or they themselves had been humiliated by home searches and road stops ... One woman said, after her husband was taken from their home because of empty wooden crates which they had bought for firewood, that the US is guilty of terrorism."

Soldiers who are set down in a country where they were told they would be welcomed as liberators and find they are surrounded by a hostile population become fearful and trigger-happy. On March 4 nervous, frightened GIs manning a roadblock fired on the Italian journalist Giuliana Sgrena, just released by kidnappers, and an intelligence service officer, Nicola Calipari, whom they killed.

We have all read reports of US soldiers angry at being kept in Iraq. Such sentiments are becoming known to the US public, as are the feelings of many deserters who are refusing to return to Iraq after home leave. In May 2003 a Gallup poll reported that only 13% of the US public thought the war was going badly. According to a poll published by the New York Times and CBS News on June 17, 51% now think the US should not have invaded Iraq or become involved in the war. Some 59% disapprove of Bush's handling of the situation.

But more ominous, perhaps, than the occupation of Iraq is the occupation of the US. I wake up in the morning, read the newspaper, and feel that we are an occupied country, that some alien group has taken over. I wake up thinking: the US is in the grip of a president surrounded by thugs in suits who care nothing about human life abroad or here, who care nothing about freedom abroad or here, who care nothing about what happens to the earth, the water or the air, or what kind of world will be inherited by our children and grandchildren.

More Americans are beginning to feel, like the soldiers in Iraq, that something is terribly wrong. More and more every day the lies are being exposed. And then there is the largest lie, that everything the US does is to be pardoned because we are engaged in a "war on terrorism", ignoring the fact that war is itself terrorism, that barging into homes and taking away people and subjecting them to torture is terrorism, that invading and bombing other countries does not give us more security but less.

The Bush administration, unable to capture the perpetrators of the September 11 attacks, invaded Afghanistan, killing thousands of people and driving hundreds of thousands from their homes. Yet it still does not know where the criminals are. Not knowing what weapons Saddam Hussein was hiding, it invaded and bombed Iraq in March 2003, disregarding the UN, killing thousands of civilians and soldiers and terrorising the population; and not knowing who was and was not a terrorist, the US government confined hundreds of people in Guantánamo under such conditions that 18 have tried to commit suicide.

The Amnesty International Report 2005 notes: "Guantánamo Bay has become the gulag of our times ... When the most powerful country in the world thumbs its nose at the rule of law and human rights, it grants a licence to others to commit abuse with impunity".

The "war on terrorism" is not only a war on innocent people in other countries; it is a war on the people of the US: on our liberties, on our standard of living. The country's wealth is being stolen from the people and handed over to the super-rich. The lives of the young are being stolen.

The Iraq war will undoubtedly claim many more victims, not only abroad but also on US territory. The Bush administration maintains that, unlike the Vietnam war, this conflict is not causing many casualties. True enough, fewer than 2,000 service men and women have lost their lives in the fighting. But when the war finally ends, the number of its indirect victims, through disease or mental disorders, will increase steadily. After the Vietnam war, veterans reported congenital malformations in their children, caused by Agent Orange.

Officially there were only a few hundred losses in the Gulf war of 1991, but the US Gulf War Veterans Association has reported 8,000 deaths in the past 10 years. Some 200,000 veterans, out of 600,000 who took part, have registered a range of complaints due to the weapons and munitions used in combat. We have yet to see the long-term effects of depleted uranium on those currently stationed in Iraq.

Our faith is that human beings only support violence and terror when they have been lied to. And when they learn the truth, as happened in the course of the Vietnam war, they will turn against the government. We have the support of the rest of the world. The US cannot indefinitely ignore the 10 million people who protested around the world on February 15 2003.

There is no act too small, no act too bold. The history of social change is the history of millions of actions, small and large, coming together at points in history and creating a power that governments cannot suppress.

· Howard Zinn is professor emeritus of political science at Boston University; his books include A People's History of the United States