On 2 November 1950, Father Kapaun made the decision that led to his death.
The Korean war chaplain was in the middle of a firefight, with the American forces overrun by Chinese soldiers outside a crossroads town called Unsan in North Korea.
Lighting forest fires to frustrate US reconnaissance planes, the Chinese surrounded the Americans and pressed in, attacking with small arms, grenades and even bayonets.
Meanwhile, Chaplain Emil Kapaun, a Catholic priest from a farming village in Kansas, gathered the wounded in a dug-out shelter made of logs and straw.
Father Kapaun in an undated photograph from Korea Though he never fired a shot, Father Kapaun saw as much mean action as any man in his unit
When American officers ordered the able-bodied to retreat, Father Kapaun, a 35-year-old captain, refused to leave the wounded.
As the Chinese soldiers began lobbing grenades into the dug-out, Kapaun negotiated a surrender.
"Father Kapaun had several chances to get out," Warrant Officer John Funston later told a Catholic priest who collected accounts of Fr Kapaun's actions in Korea, "but he wouldn't take them."
His capture and forced march northward with hundreds of other American prisoners was merely the beginning of Father Kapaun's trial, an ordeal that ended in his death from starvation, cold and lack of basic medical care at a prison camp in North Korea six months later.
For his heroism, a group of Kansas politicians are pushing to have him awarded the Medal of Honor, America's highest military decoration.
Reports of Kapaun's selfless bravery have got him short-listed for another rare high honour: the Catholic church has named Kapaun Servant of God, the first step toward sainthood, and the Vatican has opened a formal inquiry into whether he merits canonisation.
It is remembered bitterly along the Korean peninsula as a period of misery, massacres, political violence and the wholesale destruction by the US Air Force of virtually every town, city and major dam in the north.
But in the US, the conflict is little remembered, overshadowed in the American consciousness by World War II and Vietnam.
"The Korean War was forgotten almost within a year or so of its start," says Bruce Cumings, a historian at the University of Chicago and one of the foremost US experts on the conflict.
"Most Americans don't know the first thing about it."
If President Obama awards him the Medal of Honor, he will be just the fifth Catholic priest to win the award - out of 3,458 American soldiers, sailors, marines and airmen who have won it.
If he is named a saint, Kapaun will be the first member of the US military so honoured.
"He gave his life for those people that he was serving," says Father John Hotze, an investigator for the diocese advocating for Kapaun's canonisation.
"At the time of his death, he was giving his life for his fellow prisoners... and he was that example of Christ present in the world today."
A small-town boy
Those who knew him remembered him as a man's man who loved the rough army life, enjoyed bowling and talking sport with the lads, and who cared deeply for the young men under his care, be they Catholic, Protestant or Jewish.
"He was a strong, holy man and he was very determined to do what the bishop wanted him - help the boys," says his sister-in-law Helen Kapaun, 83.
"It's really hard to think of him as so brave and having so much courage and strength. Not because of what I seen in him, only because I never realised he could be that strong and holy."
Kapaun was born in 1916 to a poor family in Pilsen, a tiny farming community in central Kansas.
Like other boys, he helped out on the farm, milking cows and tending livestock and weeding the garden.
The resourcefulness, capacity for hard work and physical toughness needed to eke out a living on the prairie in the 1920s helped prepare him for the army - and the prison camp.
Life in Pilsen centred around a small Catholic church where congregants confessed both in Czech and English, and from an early age, Kapaun earned a reputation as devout beyond his years.
He left home at 14 for a Catholic boarding school run by Benedictine monks.
In 1940, at age 24, Kapaun was ordained as a priest. He soon returned to give his first Mass at the church he was raised in. Pilsen celebrated him with a procession through the town.
As American entered into World War II, other young men in town were leaving for the military. Kapaun wanted to join up as a chaplain, but his bishop refused.
Instead, he settled into a familiar, if awkward, life as a young priest in the parish in which he was raised.
"There are people here, relatives and friends, who are superior to me (in age, in school, etc.)," he wrote to his bishop, perhaps hinting delicately he thought he could better serve the church elsewhere.
"Some find it difficult to look up to me as their spiritual superior."
Eventually the bishop relented, and in August 1944, Kapaun left for Army chaplaincy training.
'A young calf'
"Army life does a person a lot of good," he wrote to his parents. He particularly enjoyed the long marches. "In the evening I feel as fresh as a young calf."
After service in Burma and India, far from combat, Kapaun mustered out of the Army in 1946.
Life back in the States seemed to bore Kapaun. He completed a graduate degree in education in Washington DC, then returned to Kansas to take a position in Timken, a small town in need of a priest who could speak Czech.
In summer 1948, Kapaun told the Army he would return to the chaplaincy if given permission.
On an Army questionnaire, he specifically requested extended duty overseas, according to his biographer William Maher.
So Kapaun again donned the uniform of a US Army officer, this time as a captain. In January 1950, he was crossing the Pacific for Japan, assigned to the 8th Cavalry Regiment of the 1st Cavalry Division.
Those men were among the first US troops to join the fight in Korea, crossing the Sea of Japan and landing at Pohangdong, South Korea, in July 1950.
"Tomorrow we are going into combat," he wrote to Bishop Mark Carroll of Wichita. "I have everything in order, all Mass stipends, my will, etc."
Within days Kapaun and his comrades were on the front lines, engaged in heavy fighting against the North Korean forces.
Father Kapaun and other US troops in Korea Kapaun, with cross on his helmet, is shown leading an exhausted soldier off the battlefield.
As a chaplain, Kapaun never appears to have fired on enemy forces personally, though he admitted to carrying a weapon at times.
But he refused to stay behind, putting himself in as much danger as any of the grunts in his unit and exhibiting awe-inspiring bravery, his comrades have recounted to Army and church investigators.
"He came to me when I was in charge of setting up headquarters and asked if he could say Mass for the men in that area," Captain Joseph O'Connor recalled in 1954.
"I said, 'Father, things are pretty hot here at present and I don't think you should be up here.' Father said, 'Then I think we need a Mass, Captain'."
He also administered last rites to countless dying soldiers, helped bury American and enemy dead, and wrote personal letters to the families of fallen soldiers.
"I have been on the front lines for eight days. We were machine gunned, hit by mortars and tanks," he wrote to friends in Timken, Kansas.
"Three times we escaped with our lives... God has been good to me. Others have not been so fortunate. There are many horrors in war. A fellow can only stand so much."
During a battle on 2 August 1950, Kapaun and another officer ran across the no man's land between the lines, dodging intense machine gun and small arms fire, to rescue a wounded soldier. For his efforts, Kapaun was awarded the Bronze Star, one of the highest combat decorations in the US military.
'Turned into animals'
On the night of his capture at Unsan, Kapaun, about 15 to 25 wounded who could still walk left the dug-out at gunpoint and joined hundreds of American prisoners on a long, desperate forced march northward, deeper into North Korea.
Many of the men were too hurt to walk, and the Chinese soldiers abandoned anyone who fell behind to freeze to death.
Survivors said that Kapaun, even as he was suffering frostbite on his feet, helped carry wounded men in litters hundreds of miles, shaming recalcitrant comrades into helping.
Eventually, Kapaun and his fellow captives were imprisoned in a camp near Pyoktong, just south of the Yalu River. Dozens had fallen behind and died along the way.
There, the Chinese and Korean captors held them in freezing and near-starving conditions.
Kapaun sneaked around the camp stealing food - grain, potatoes, salt, peppers and garlic - from the Chinese stores, and fed his comrades from his own meagre rations.
He tended the sick and wounded, bathing them and washing their clothes, day after day as conditions only worsened and more and more men perished.
He served as a moral exemplar, survivors said, persuading the sickest and most miserable not to give up.
"By February and March, the majority of us had turned into animals, were fighting for food, irritable, selfish, miserly," recalled Captain Robert Burke in a 1954 letter to Father Arthur Tonne, a Kansas priest who compiled anecdotes about Kapaun.
"The good priest continued to keep a cool head, conduct himself as a human being, and maintain all his virtues and ideal characteristics.
"When the chips were down, Father proved himself to be the greatest example of manhood I've ever seen in my life."
Through it all, the chaplain stubbornly refused to renounce his faith.
He defied and confronted the guards during forced indoctrination sessions. At risk to his own safety and life, he would sneak about the camp to comfort and encourage the young enlisted men and hold secret prayer services.
One survivor told Maher how Kapaun would carry a bucket on his furtive jaunts about the camp, to make it look as though he were on a chore if confronted.
"By his very presence, he could turn a stinking mud hut into a cathedral," the survivor, Lt Raymond Dowe, recounted to Maher.
With little food, poor sanitation and almost no medical care, Kapaun's health deteriorated. By early spring he was limping from a blood clot in his leg and wore a patch over an infected eye.
He contracted dysentery and pneumonia. After months in near-freezing and starving conditions, Kapaun died in late May 1951.
"In his last hour he heard my confession," a comrade named Felix McCool recalled in a letter to Father Tonne.
"Father Kapaun said: 'As you see, I am crying too, not tears of pain but tears of joy, because I'll be with my God in a short time.'"
Road to sainthood
Under US law, the Medal of Honor must be recommended to the US president within two years of the deed and awarded within three years of the date of the deed.
The campaign to recognise Kapaun comes as the White House said on Monday that President Obama would award a posthumous Medal of Honor to another US serviceman, Leslie Sabo, for his heroics during the Vietnam War in 1970.
Sabo, 22, was recommended posthumously for the nation's highest award, but the citation ended up lost in military bureaucracy and was forgotten until 1999.
Stories of Kapaun's heroics at the battle of Unsan began to trickle out right away, but his deeds at the prison camp remained mostly untold until 1953, when the North Koreans released the surviving Americans from Pyoktong.
In recent years, members of Kansas's congressional delegation began lobbying their colleagues to waive the Medal of Honor time limit for Kapaun.
The exemption was signed into law in December, and in January, the six congressmen and senators asked Secretary of Defense Leon Panetta to recommend that President Barack Obama award the medal - the penultimate step in a long bureaucratic process.
"He was an amazing man in multiple dimensions - in his life as a chaplain... and its intersection with his duty as a military leader," says Kansas Congressman Mike Pompeo.
"The two come together in these incredible stories of heroism at this difficult moment in our nation's history. He did this in a way that is so unique: not seeking glory or for himself, but always in service."
It is unclear when or whether Mr Panetta and Mr Obama will award the medal, but Mr Pompeo says he is confident.
Meanwhile, the effort of Father Hotze and the diocese of Wichita to win canonisation for Kapaun, which Father Hotze launched in 2001, has moved to Rome. There, the Vatican's Congregation for Saints will carry out its own investigation.
Father Hotze speculates Kapaun was just a selfless individual whose natural inclination was to give what he had to others, including his energy and effort.
But on the front lines and in the prison camp, that quality was magnified to heroic proportions because of the horrific situation in which it was expressed, Father Hotze says.
"He knew he was going to die, he had the courage and strength to realise a better way to face death is to realise you have helped these other people," he says.
"Even the heroic actions that he took they are not beyond the ability of any one of us. Each and every one of us can offer clothes, food, comfort, encouragement.
"He shows us that we too can be great, we too can be saintly people, based on our day-to-day actions."
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In his own words
- 11 July 1950: "Tomorrow we are going into combat. I have everything in order, all Mass stipends, my will, etc."
- 7 August 1950: "I have been on the front lines for eight days. We were machine gunned, hit by mortars and tanks. Three times we escaped with our lives... God has been good to me. Others have not been so fortunate. There are many horrors in war. A fellow can only stand so much."
- 8 August 1950: "My, how nice it would be to sleep in a bed. These fox holes are anything but comfortable but they feel good when the enemy shells start bursting around us."
- 11 August 1950: "This fighting is nerve-racking. Many of my soldiers crack up - they go insane and scream like mad men. It seems like a dream. I don't know if I will live through the day or night. We are close to heaven but really we are more like in hell."
- 25 September 1950: "I thank you for all the prayers, etc. My boys need them worse than I do, for some way or another I have not been hit... A fellow's nerves take an awful strain and a fellow surely can pray when these big shells explode around the area. It is no fun."
- 16 October 1950 (Kapaun's last letter): "God has been very good to us and we are still alive."