As the man and woman walked slowly towards the war memorial in Chicago last week, the figure of Barack Obama was instantly recognisable. But as the pair hugged after laying a wreath in the ceremony, it was the young woman who caught the attention of the media and whose photograph flashed around the world.

It was difficult not to notice her. As the President-in-waiting embraced her, it was clear that she was a double amputee. Rarely has the human cost of America's war in Iraq been so painfully and poignantly illustrated.

The woman was Tammy Duckworth, one of the most remarkable figures to emerge from the conflict. Horribly wounded by an insurgent attack, the former helicopter pilot is now part of a wave of Iraq and Afghanistan war veterans who are returning home and reshaping US politics. They are running for office, heading government departments and campaigning on issues they care about.

Duckworth is now one of the most visible and high-profile among them. There are even whispers that she might replace Obama in the Senate, taking the seat left vacant when he moves to the White House, or that he might appoint her to his cabinet as head of the Department of Veterans' Affairs. But on that cold Chicago morning last week, as Duckworth and Obama paid tribute to America's war dead, it was not politics that were on Duckworth's mind. It was her former comrades-in-arms, recently redeployed back to the country where she lost her legs. 'I was actually thinking about my crew,' she told The Observer.

Last week marked a doubly poignant anniversary for Duckworth, a petite and pretty half-Asian woman with a homely Midwestern accent. Veterans of all wars were remembering their fallen comrades on 11 November, but the day after was Duckworth's 'Alive Day', the fourth anniversary of her close brush with death.

The Alive Day is a tradition that sprang up in Vietnam as wounded American soldiers struggled to cope with the physical and emotional scars left by the injuries of war. Now Duckworth is part of a new generation treading the same path and marking a fresh wave of Alive Days. For Duckworth, 40, commemorating the day that left her so horribly wounded was a bitter-sweet moment.

'It could be a horrible day, but I choose to celebrate it. Every year we kind of have a big party. I know it's the day I lost my legs, but it is also the day that I survived and got my life back,' she said.

On 12 November 2004, Duckworth was a helicopter pilot in the Illinois Army National Guard. She had persuaded her superiors to send her to Iraq when her unit was shipped out, just as she was about to be transferred elsewhere. On that fateful date she had piloted her 'bird' over Baghdad from landing zone to landing zone.

Her final stop had been in the green zone, where she had picked up milkshakes, stir-fry food and Christmas decorations. Once back in the air, she heard the sound of bullets hitting the chopper. 'I remember hearing the tap-tap of small-arms fire. I was reaching over for the GPS to record the location and then there was a giant fireball,' she said.

The chopper had been hit by a rocket-propelled grenade fired by an insurgent. Unaware of the extent of her injuries, Duckworth tried to help her fellow pilot, Dan Milberg, guide the stricken craft down. But as she struggled she wondered why the pedals were not responding to her commands. It never occurred to her that she no longer had any feet with which to press them. 'I did not realise my legs were already gone,' she said, with a lightness of tone that belied the full horror of what she was describing. 'I mean, how many times a day do you ever look down to check if you still have your legs?'

The helicopter hit the Iraqi dirt and Milberg dragged her to a second aircraft for evacuation. Her injuries were so bad that Milberg mistakenly assumed she was dead. Instead she woke up eight days later at the famed Walter Reed military hospital back in the US. Her husband, Bryan Bowlsbey, had been at her side for days, repeating a mantra-like chant to her as she lay unconscious: 'You were injured. You are at Walter Reed. You are safe.'

So began Duckworth's new life. Like thousands of injured Iraq veterans before and after her, she faced months of painful physical therapy and the mental anguish of coping with her loss. But for Duckworth, her energies gradually began to focus around veterans' rights and their health issues.

Walter Reed is a regular stop on many politicians' rounds as they make trips both private and public to visit the wards. Soon Duckworth found herself making contacts with politicians such as Senator Richard Durbin, Senator Obama and Congressman Rahm Emanuel.

It was Durbin in particular who persuaded the feisty and outspoken veteran to consider entering public life. It was a long process. By March 2005 she was taking her first steps on her artificial limbs. Learning to walk again was her priority. But by that summer Durbin wanted her to run for office as a Democrat in a local congressional seat in 2006.

'I did not know if I wanted to put up with entering public life. It is not an easy thing to do,' she said. 'But then I realised that I spent all this time complaining about things not being done right for the troops. Why not change the laws yourself? I like challenges and I thought, "it's easy to complain, but it's not so easy to change things".' She made the decision to get involved. It could yet end with her as a high-profile face in the new Obama administration.

Changing things is now Duckworth's focus. She ran for Congress in Illinois, eventually losing a nail-bitingly close race in a previously solid Republican seat. Then she became director of Illinois's Department of Veterans' Affairs, where she has raised the profile of veterans' needs, especially the problems they face getting jobs when they return from duty. She has testified before Congress regarding medical care and employment for returning veterans and spoke at this August's Democratic party convention.

In 2006 she delivered an official Democratic response to one of President Bush's weekly radio addresses to the nation. In it she lambasted his policies on Iraq and the path the White House took in going to war. 'Instead of a plan or a strategy, we get shallow slogans like "mission accomplished" and "stay the course",' she said in the broadcast. Now political office in Washington may be beckoning her.

Duckworth said she was flattered that her name was being bandied about, but insisted that she has had no talks with anyone about either a Senate seat or cabinet post. However, she does say she is willing to serve if asked.

'I have been in the army for 18 years and when my commander-in-chief asks me to do something, I just grab my helmet,' she said. 'If I was willing to go to Iraq for Bush, I would be willing to serve in any capacity for Obama that he asked me to.'

That sort of military attitude has defined Duckworth's life. Perhaps it also gave her the strength to overcome her injuries. She was born in Thailand, the daughter of an American father and a Thai-Chinese mother. She joined the army reserves at college and chose to train as a helicopter pilot because it was one of the few military jobs that could place a woman directly in combat. She later joined the National Guard as she took a day job as a manager with Rotary International.

Amazingly, she displays no bitterness towards the war in Iraq. 'Anger is such a waste of emotion. It is not worth it. I am moving on ... I am not going to pick at that scab. I learned in hospital not to pick at scabs,' she said.

Duckworth believes firmly that the war was based on false intelligence and that the American public was sold lies. But it still does not make her regret serving there. 'That does not diminish the honour and service of my buddies and me. I would go back to Iraq if I could,' she said.

In her dreams, she still does. Duckworth has a recurring dream that is becoming less frequent now, but is often triggered by news reports from Iraq on television. In it she has her legs back and is flying her chopper again. 'I go to sleep and in my dream I wake up in Iraq. I get up and fly my missions. I live an entire day. At the end I am exhausted and I go to sleep. When I wake up I am in Illinois,' she said.

The dream carries with it a mixed bag of emotions. 'I am happy because I am flying again and I have my legs and I am doing my job,' she said.

But for Duckworth, her experiences on the battlefield have changed that job for ever. She now has a fresh mission, one that has already taken her into the heart of American political power, carried on new legs of steel.

Presidents and presidential contenders whose military records helped propel them to the political front line

John McCain

McCain was a navy pilot from a distinguished American military family. He was shot down over Vietnam and spent five years as a prisoner of war. He was beaten and tortured and emerged a hero. His war record led him into politics and was enough to win him a Senate seat and this year the Republican nomination for president.

John Kerry

The Senator from Massachusetts was picked as the Democratic nominee for president in 2004. His record as a Vietnam veteran, on the dangerous Swift boat missions, should have shored up his credentials but instead came under fire and 'Swift Boating' entered the political dictionary as a description for dirty tactics.

George Bush

The elder Bush was a veteran of World War Two who flew dangerous bombing missions against the Japanese in the Pacific. On one mission his plane was hit by enemy fire and set ablaze. Bush guided the stricken craft to complete his bombing run and then bailed out. He was rescued by a submarine.

Theodore Roosevelt

The dashing two-term president of the early 20th century was an action hero come to life. An avid hunter and outdoorsman, he rode to the White House on a wave of public support after his heroics in the Spanish-American war of 1898. Roosevelt is the only president to have been awarded the Medal of Honour, America's highest military honour.

Abraham Lincoln

Perhaps America's most loved, famous and respected president, Lincoln is known for his civilian leadership and victory in the Civil War, though he did serve three short tours in the Black Hawk War of 1832 in Illinois, one of many conflicts with Indians as the country expanded westwards. He later wrote he had not had '... any such success in life which gave him so much satisfaction'.

George Washington

America's founding president also led the country's military victory against the mighty British Empire. He led the colonists' Continental Army to victory in a war that lasted from 1775 to 1783. He was an inspiring leader and master tactician who also fought in the French and Indian War in the 1750s. He remains the only president to have been elected with 100 per cent of the electoral college votes.