Editor's Note: This is the third in a five-part series.

The sea was slick with oil, littered with debris, and crowded with panicked men who moments before had been aboard the S.S. Van Warwyck when it came under attack.

But there in the water was a dog, swimming to the foundering men, guiding them to floating pieces of the wreckage or letting them hold on to her back while she herself swam them to safety.

It was June 26, 1944. The men were prisoners of war and so was the dog. Her name was Judy.

She too had been aboard the ship, and in an effort to save her life, her adoptive caretaker, Leading Aircraftman Frank Williams of the Royal Air Force (RAF), had pushed her through a 10-inch porthole and into the water 15 feet below. He then lost sight of her as he made his own escape. For more than two hours, he swam amid the chaos and debris, searching for her.

Judy, a purebred liver-and-white English pointer, had been born seven years before in Shanghai, where she had become a mascot for a British Royal Navy ship based there. By January 1942 she was aboard the H.M.S. Grasshopper, a 585-ton gunboat stationed in Singapore, when the Japanese took that city. The boat managed to escape the harbor and sail for the Dutch East Indies. It was reportedly two miles from safety when it was bombed by Japanese planes and the passengers had to abandon ship.

The survivors were marooned on an island in the South China Sea for two days without food or water, and it was Judy who led them to a freshwater spring, sniffing it out during low tide and digging under the sand to bring the drinkable water up to the surface.

Unfortunately, after commandeering a Chinese junk that took them upriver into Sumatra and then hiking 200 miles across the island, the men, with Judy in tow, unknowingly wandered into a Japanese village and were captured and marched to a POW camp.

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Refusing to leave her behind, the men smuggled Judy with them, keeping her hidden behind rice sacks and away from the eyes of their captors. Eventually, they ended up in the Gloergoer POW camp in Medan, Indonesia. And it was there that Judy met Williams in February 1942.

He'd been watching the dog since his arrival at the camp, eyeing the way she hunted for food, snapping up the maggots the men would toss from their bowls. He saw that, although she was always a welcome presence among the prisoners, she didn't belong to any one man. One day he called her to him and held down his bowl of rice, giving her the whole of his portion. When she was finished eating, she lay by his feet and didn't leave. From then on she was Williams' dog.

Judy quickly earned herself a reputation as the protector of not only Williams but of all the prisoners in the camp—garnering the appreciation of the men and the disdain of the prison guards.

The uplift she afforded the POWs alone was enough to draw the ire of their Japanese captors, but it was the way she fearlessly intervened when the guards would beat a prisoner that put her hazardously close to death. Without hesitation she would fly to the side of the man taking the beating, snarling and growling to protect whomever it was, which usually meant the guards would pause from hitting the man and turn their aggression on the dog, hitting her with the butts of their rifles.

Knowing that this wouldn't be tolerated for long, Williams believed that the only way to keep her from being shot was to get her official POW status. And so he devised a plan. He waited for the camp's commandant to get his fill of saki, knowing the Japanese officer was a happy, pliable drunk. Williams's calculation—and nerve—paid off; the commandant agreed and from then on Judy was POW 81A.

Although this new distinction did save her from execution on multiple occasions, Judy was never out of danger for long. Over three long years as a POW, she provoked prison guards and the wild animals she encountered in the jungle surrounding the camp, barking at tigers and surviving a battle with a crocodile.

And then in June 1944, after the prisoners were herded onto the doomed Van Warwyck, she—and Williams—managed to survive yet again, although they were soon recaptured by the Japanese and held until the end of the war.

View Images In 1946 the British government awarded Judy the Dickin Medal, which honors the extraordinary wartime service of animals. PHOTOGRAPH BY TOPICAL PRESS AGENCY/HULTON ARCHIVE/GETTY

When they were finally liberated in August 1945, Williams thought his days of hiding Judy were over—that they were finally free, not only of interment and beatings, but also of the fear of being separated. But he was wrong.

When they arrived at the dock to board the S.S. Atenor, the ship that would deliver them home to Britain, he noticed a sign forbidding any animals from boarding the ship. To leave her behind now was inconceivable. The other men from the camp went into action and held the dog back while Williams went aboard. Then they distracted the guards and smuggled Judy onto the ship.

Eventually, they made it home to England together, where they were met with fanfare and fame. Judy was awarded the United Kingdom's Dickin Medal, which honors the wartime service of animals. In February 1950, she contracted cancer and died at age 13. Williams buried her in a specially made RAF coat.

Williams said that every day in the prison camp he thanked God for Judy because she gave him a reason to keep living. "All I had to do was look at her and into those weary, bloodshot eyes," he said, "and I would ask myself: 'What would happen to her if I died?'''

Coming tomorrow: Left Behind in Vietnam

Rebecca Frankel is a senior editor at Foreign Policy Magazine. Her book, War Dogs: Tales of Canine Heroism, History, and Love, will be released in October.