Twenty years ago this Friday, on the 50th anniversary of the D-Day landings, I was standing on a cliff-top overlooking the Normandy beaches on which so many men had died half a century earlier.
It was a deeply moving experience, looking down at the immaculately-choreographed ceremonies, and trying to imagine the carnage, terror and mayhem of the landings themselves. There can surely be few more total contrasts than between the reality of a battle and the commemoration of it so many years later.
By definition, those who mark these anniversaries are the survivors - and that means not only those who survived physically but also those who survived mentally. For every veteran proudly wearing his medals and remembering fallen comrades, there are others who wish they could forget. They are the ones whose war wounds are invisible.
When in years to come, US military veterans gather to remember the war in Afghanistan (2,000 US dead, 20,000 wounded), Sgt. Bowe Bergdahl is unlikely to join them. He's the US soldier who was freed by the Taliban last weekend after nearly five years in captivity in return for five Taliban detainees freed from Guantanamo Bay.
According to the US military, "there are legitimate concerns about Bergdahl's physical and mental health" - so much so that even his family have been warned that he's in no fit state yet for a reunion. Judging by the video of his handover released by the Taliban - and with all the caveats about not making medical diagnoses based on sketchy video evidence - he may well be deeply traumatised by his ordeal.
Sgt. Bergdahl is reported to have walked away from his unit in Afghanistan on 30 June, 2009, five days after his battalion suffered its first casualty, a man to whom Bergdahl was reported to have been close. According to a report in the New York Times, "he left behind a note in his tent saying he had become disillusioned with the Army, did not support the American mission in Afghanistan and was leaving to start a new life."
The Washington Post yesterday quoted villagers who live close to the base where he was posted as remembering him walking through the village in a haze. "To them, it's clear something was wrong with the American. And he seemed to be deliberately heading for Taliban strongholds, they say."
Is Bergdahl a deserter? A traitor? Is he, as some critics in the US have implausibly suggested, a real-life incarnation of Nicholas Brody of the TV series Homeland, a captured US serviceman who may have switched sides? Or is he one more casualty of war, a man whose wounds can't be seen but are real nonetheless? It's perfectly possible, of course, to be both.
In 2012, more serving members of the US military committed suicide than were killed in action. Even more appallingly, 6,500 former military personnel committed suicide in the same 12-month period. In the UK, more British soldiers and veterans took their own lives in 2012 than died fighting in Afghanistan over the same period.
Post-traumatic stress is now a recognised medical condition. The military know the dangers, and, in so far as they can, they try to offer support for servicemen and women who need help. Even so, in both the UK and the US, it's estimated that more than one in 10 people who are homeless are military veterans.
Until relatively recently, the long-term human cost of wars to those who fight in them was something that both political and military leaders were anxious not to confront. It is harder to convince a country of the need for war if people know that even those who escape death or injury by bomb or bullet may still be scarred for life.
That's probably why there's been such an outcry from President Obama's political opponents over the deal to free Sgt. Bergdahl - it is an unwelcome reminder that wars are messy, nasty and cruel, and that they can often lead to good people doing bad things.
So should all wars be opposed, on principle? Are we all pacifists now? Or do we need to ensure that on those rare occasions when all available alternative policy options have been tried and failed, the men and women who are sent into harm's way are properly cared for, both on and off the battlefield?
Two thousand years ago, the Roman poet Horace wrote "Dulce et decorum est pro patria mori" (It is sweet and honourable to die for your country). In 1917, in a poem using Horace's aphorism as its title, the First World War poet Wilfred Owen called that a lie. Addressing the reader, he wrote that if you had seen, as he had, the horrendous effects of a gas attack:
"My friend, you would not tell with such high zest
To children ardent for some desperate glory
The old Lie: Dulce et decorum est
Pro patria mori."
I shall be thinking of those lines as I watch the 70th anniversary D-Day commemorations -- and as I ponder the fate of Sgt. Bowe Bergdahl.