(CNN) -- As the world recovered from its second world war, Hemingway ended his third marriage, divorcing Martha Gellhorn, and in 1946 married Mary Welsh.

But Hemingway's fourth marriage, like the others, had its share of problems. According to accounts, the couple argued constantly, and Hemingway's wandering ways apparently never ceased.

As the 1950s approached, and despite the fact that he was one of the most recognized faces on the planet, Hemingway's fiction was suffering criticism, too.

"There was some thought that Hemingway's career had exhausted itself and it was pretty much over," says Hemingway scholar Dr. James Nagel.

That, it turned out, was far from the case. Hemingway, living in Cuba, was at work on an encompassing novel about the sea. Nagel says when he sent it Scribner's, they sent it back claiming it was unpublishable.

But they did like the last part, a story about an old Cuban man and his battle with a monster marlin.

Hemingway's longtime friend and boat captain, Gregorio Fuentes, was said to be the inspiration for the main character in "The Old Man and the Sea"

When it was published as a novella, "The Old Man and the Sea" was an instant success, topping the best-seller list, and some critics called it a classic. It was also the ultimate exhibition of Hemingway's writing -- sparse, subtle, streamlined prose resonating with power.

"The Old Man and the Sea" won the Pulitzer Prize in 1952. In 1954, Hemingway was awarded the Nobel prize for literature. It was the high point of Hemingway's writing career, ensuring his legacy for generations to come.

"I think he would not be the celebrity he is still today were it not for 'The Old Man and the Sea' and the two prizes," says Nagel.

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But Hemingway was unable to attend the official Nobel ceremony, as he was still recovering from an event that some say began his downward spiral to death seven years later.

While on safari in Africa in '54, Hemingway and wife Mary were involved in a plane crash in the African bush. Suffering injuries that weren't life-threatening, the group eventually managed to call another plane. But after picking up Hemingway and company, the second plane crashed on take-off.

The news couldn't have been worse -- papers around the world reported that Hemingway had been killed. Hemingway, who seemed to have been obsessed with death in his prose, had found it in life.

On Hemingway While living in Cuba, Hemingway wrote blood pressure counts, weight and other medical information on his bathroom walls.

Of course, the news was incorrect. Everyone survived the crash. Mary suffered broken ribs, and among Hemingway's many injuries, "he lost virtually all kidney function for the rest of his life," says Nagel. "Because of the loss of kidney function, he got high blood pressure. He was given a drug for high blood pressure that has depression as a side effect."

Toward the end of the 1950s, it was apparent to many who visited the legendary writer that he was reaching a crisis point -- he was described as withdrawn and moody, at times suffering from delusions. Numerous theories were developed, and are still maintained.

One centers on the idea that Hemingway was upset because he could no longer write well. Another claims, as Nagel says, that he was "depressed because he saw the black emptiness of human existence, or something philosophical."

Nagel says the blood pressure medication combined with the shock treatments that Hemingway underwent for his depression may have been partially responsible for his mood swings.

On Hemingway When traveling from the U.S. to Europe, Hemingway crossed the Atlantic on ocean liners. He made as many as four voyages a year and more than 30 in his lifetime.

Beginning in 1960, "they gave him 36 shock treatments at the Mayo Clinic in Rochester, Minnesota, and shock treatments back then were very severe," Nagel says. "They caused serious memory loss in Hemingway. If there's anything a writer can't stand, it's the loss of memory. After some of those shock treatments he didn't even know his name. Then he would be sent back home to recover, given that drug for high blood pressure, and it was only a matter of weeks before he was depressed again."

The slow decline was evident in Hemingway's physical condition -- he had dropped in weight to 160 pounds from the 200-plus pounds he weighed in his prime, according to Nagel.

But the treatment went on, as Hemingway showed continued signs of stress.

"He would get on his knees and cry and beg his wife not to send him back for more shock treatments," Nagel says.

When he wasn't at the Mayo Clinic, Hemingway was spending time at his home in Ketchum, Idaho.

Hemingway in Malaga, Spain, 1959

"It was on the first day he returned from his 36th shock treatment that he killed himself," Nagel says. Hemingway had earlier convinced doctors that he could return home. On July 2, 1961, Hemingway put a shotgun to his head and pulled the trigger.

The suicide was the story for the next two weeks as the world mourned the passing of an icon and tried to comprehend the ambiguous legacy he left behind.

Hero, adventurer, father, womanizer, friend, enemy, celebrity -- as Hemingway scholar Michael Reynolds sees it, Hemingway would have been none of these things if he hadn't had talent.

"By the time we've reached the centennial (of his birth) he's been reduced to generalizations and clichés," Reynolds says. "But the fiction ... if he didn't write anything, we wouldn't remember him."