"Ask not what your country can do for you - ask what you can do for your country."
John F Kennedy
Pat Tillman was a young American footballer who woke up one morning and decided that sport was trivial. He came from a military family, his country was now at war with an opaque and ruthless enemy, and he felt helpless. "I play football, and it just seems so unimportant compared to everything that's taken place," he said after watching the collapse of the twin towers on television. "My grandfather was at Pearl Harbor and a lot of my family has gone and fought in wars, and I really haven't done a damn thing . . ."
In 2002, Tillman, who was then 25, renounced his career in the National Football League, and an annual salary of more than $1m, to enlist in the 75th Ranger Regiment. It was as if the words of John F Kennedy, resounding across the decades, had spoken directly to him. He knew that, following the events of 11 September 2001, his mission no longer lay on the football fields of America, where he played for the Arizona Cardinals, but on the battlefields of Afghanistan and Iraq, as a foot soldier in his country's war without end.
Many Americans rejoiced when they discovered that Tillman was to become a soldier. He was celebrated as a true hero, a gleaming symbol of simple, unquestioning American patriotism, and the first professional sportsman to volunteer for military service in more than 25 years. What Tillman did was certainly brave: it is hard to think of a contemporary English sportsman who would take a similar risk, swapping the life and ease of a sporting plutocrat for active service in Iraq.
"There is in Pat Tillman's example," said the Republican senator John McCain of Arizona, "in his unexpected choice of duty to his country over the riches and other comforts of celebrity, and in his humility, such an inspiration to all of us to reclaim the essential public-spiritedness of Americans that many of us, in low moments, had worried was no longer our common distinguishing trait."
On 23 April, Sergeant Tillman was out on patrol in the mountainous, thickly forested borderlands of western Afghanistan when insurgents ambushed his unit. In the ensuing firefight, he was shot and killed, and in that instant became the latest, and most famous, victim of America's war against terror.
I was in New York when news of Tillman's death became known to the public. It was, by strange coincidence, the weekend of the NFL draft at Madison Square Garden. This is the event at which the best young American footballers discover exactly for whom they will be playing as full-time professionals, and it is usually an occasion of grand celebration. But this year's event, which began with a minute's silence in memory of Tillman, was sombre. There had been a death in the family, but at least, it was said, Tillman had died to protect the freedom of all Americans.
Or had he? As Iraq hurtles towards total anarchy, as the killing in Afghanistan continues, as Iraqi prisoners of war are humiliated and a kidnapped American is beheaded, as Blair staggers and Bush swaggers, Tillman's death is increasingly being seen in his own country less as an act of heroic duty than of useless sacrifice. His loss, wrote the US sports journalist Rick Reilly, "shook the country like no other in this war . . . that continues with no just reason".
Tillman was sincere. He believed in the possibility of America, in its power and optimism, and its freedoms. He believed, as his grandfather had before him, that it was noble to die in the cause of a just war.
"There's more to life than football," he would tell his friends, and he was feted for saying this and for acting according to his own code of honour. But there is not more to death than football. There is only death. The football goes on, of course, but it must now go on without US Army Ranger Pat Tillman.
Hunter Davies returns next month