IN MAY 2003, President George W Bush addressed the world from the deck of the USS Abraham Lincoln off the coast of California. Major combat operations of the Iraq War were at an end, he said, its tyrant Saddam Hussein had fallen and the country was free at last. Behind him, draped on the bridge of the warship, was a banner that would later become infamous. It said: “Mission Accomplished.”

In declaring what he thought had been a famous victory, President Bush also spoke about some of the great American battles of the past – the Normandy landings and the Battle of Iwo Jima during the Second World War. Decency and idealism had turned enemies into allies 70 years ago and it could do the same again in Iraq, he said. Disorder would be turned into order, Iraq would be rebuilt and Americans could return home knowing they had done a good job.

We all know what happened next. What Bush portrayed as a mission accomplished was in fact only a job half-started and in many ways one that had already been botched. And, far from heading home to celebrate, American troops became bogged down in Iraq for years. And was the glorious example of America’s role in the Second World War really as glorious as Bush suggested? Could the truth be that in Iraq, America was just repeating the mistakes of the past?

That is essentially the theory behind a new book by the Scottish historian Susan L Carruthers, The Good Occupation. America has constantly told itself that it has always been a virtuous overlord, she says, based mainly on what is seen as the “good occupation” of Germany and Japan after the Second World War. But Carruthers says the reality was different.

Using letters, diaries and other official records, the professor of history at Rutgers University in Newark, New Jersey reveals that for millions of servicemen and women, the dates that mark the official end of conflict – VE Day on May 8, 1945 and VJ Day on September 2 – were not the end. Many soldiers were stuck in service for months or years afterwards and morale, discipline and efficiency all suffered. There was looting and corruption, with the soldiers also defying the rule on non-fraternisation with the locals. In fact, sexual relations between the Americans and people in the occupied territories were so common that one soldier quipped that it didn’t take long for VE Day to become VD Day. Another wrote in a letter from Germany: “You’d be surprised to know what you can get for a bar of chocolate here in Augsburg.”

The occupations were also far from efficient. In most cases, the planning was woefully out of date or useless; there was a lack of the necessary experience among the troops and also a lack of some of the basic supplies that were needed to begin the rebuilding. And look at the long-term legacy: Germany and Korea divided. As president Harry S Truman put it: Peace is hell.

Carruthers, who was born near Irvine in Ayrshire but has lived in the US since 2002, says she first became interested in the subject of the American occupations of Germany and Japan when she was looking at the first wave of documentary films that emerged after the Iraq war.

“I was struck by the fact they had so much trouble even knowing how to name or describe what was going on there,” she says. “There was a lot of reticence about the word ‘occupation’ even though that was quite obviously what it was. I was also struck in the six months leading up to the invasion of Iraq in 2003 by the way in which we were constantly being told ‘the United States has done this before – look at the good occupations of Germany and Japan’. Lots of historians, quite rightly, pointed out that this analogy simply didn’t hold water – but as the years have gone by and it’s become ever more clear that the situation in Iraq has been a complete disaster, it seems almost as if the past occupations shine ever brighter.”

Carruthers’s book lays out the truth. Reading the letters and papers, she says she was struck by the fact that nobody in the 1940s seemed to feel they had been well prepared for the occupation of Germany or Japan. “There was planning and training schools,” she says, “but when you get to these places on the ground, they weren’t the places the guys were studying and the totality of war was such that studying pre-existent plans was not good enough for cities that had almost been completely obliterated. Time after time, the men who were sent there said, ‘Nothing had prepared me for what we found, the devastation.’”

For many, it was a traumatic experience, trying to find some order and humanity among the bombed-out, flattened remains of civilisation, and for those who were sent to the former concentration camps, it was particularly horrific. One soldier, Clifton Lisle, recorded his experiences of the camps in his diaries: “Piles of the new dead being sprayed with a hose, then buried. Masses of rotting bodies, stark naked. Thousands more dying in the wards.” Perhaps it was no surprise that many GIs felt the Germans should be punished and used that feeling to justify some of their behaviour: the looting, the corruption, even the rape of German women.

Carruthers says it was inevitable that sex was part of the occupation: people sold their possessions and their bodies. “Everywhere American occupying forces went,” she says, “barely before they had taken their boots off – in some cases no doubt while they still had their boots on – they were sleeping with local women.” The high command was not pleased about it of course and tried to ban “fraternisation” although even they were not immune – in October 1945, Time magazine reported a “striking number of higher-rank officers in residence with mistresses of vanished Nazi bigwigs”. Carruthers also quotes a more humble soldier, known only as Eddy: “We’ve got a nice deal again after our latest move,” he says. “I’m shacking up with the sweetest thing … It’s the same with all the guys. All Germany is one big whorehouse.” And there was an even darker side: a letter from infantryman Bill Taylor refers to a mass rape in Stuttgart.

Carruthers’s theory is that all of this, and all the other negative consequences of occupation, are inevitable; in fact, she is pessimistic about whether a good occupation could ever be possible, then and now. “There is always the paradox of one imposing democracy at gunpoint,” she says. “Local people would constantly point out the chasm between the rhetoric of occupation – ‘we’re reconstructing you to be good democrats, to have proper parties and parliamentary procedures’ but all of this was being done by force so it doesn’t quite add up.” She says she hopes the message of her book is that good occupations of the Second World War are a myth.

She would also like Americans to think again about the positive and affirming visions of occupation that have existed since the Second World War and use the reality as a brake on future misadventures. “To me, the lesson would be not to invade and occupy other countries,” she says. “Clearly, after Germany and Japan had been defeated, there was a need for some kind of external intervention to at least deliver food and humanitarian supplies, but would Japan and Germany look very different if they hadn’t been subject to those occupations? Maybe not, but my take-home would be one occupies anywhere else at one’s peril and this book should give one pause – even under what would seem the ‘optimal’ conditions. All these grubby things emerge because they are bound to emerge when one party is foreign to the other and enjoys a complete monopoly on power – this is a situation that one would surely not wish as a matter of choice.”

Carruthers hopes that in the future America may one day acknowledge this reality as a way of avoiding any future misadventures and repairing its reputation. She quotes one journalist Roi Ottley who reported that the US occupations of Germany and Japan had turned America into the most hated country in the world and that the behaviour of the America GI had greatly contributed to the problem. She also relates how at the end of the Second World War, General Douglas MacArthur addressed his troops on board the battleship the USS Missouri and spoke of the stars on the American planes overhead standing out like a beacon. Seventy years later, President Bush did something similar on the USS Abraham Lincoln. Will America ever learn the lessons of war and occupation?

The Good Occupation: American Soldiers and the Hazards of Peace by Susan L Carruthers is published by Harvard University Press, priced £22.95.