Ernest Hemingway was a Nobel and Pulitzer Prize-winning author who wrote in his own unique style and left behind a lasting body of work. However, some aspects of his life haven't received as much attention. He had an unusual upbringing, concocted outlandish war plans, was the subject of government surveillance and signed up to work with two intelligence agencies. Here are 10 things you may not know about this famous American writer:

 He and his older sister were raised as twins

When Hemingway was a toddler, his mother decided to raise him and Marcelline, his 18 months older sister, as twins. The two switched between living as boy twins and as girl twins, but always mirrored each other. They were dressed in similar clothes, sported matching Dutch boy haircuts, and played with identical dolls and air rifles. This treatment continued for years; Marcelline was even held back in kindergarten so she and Hemingway could be in the same class.

This forced twinning didn't foster a lasting bond — as adults, Hemingway came to loathe his sister.

He was an asset for both Soviet and U.S. intelligence

KGB files reveal that late in 1940, the Soviet intelligence agency NKVD — the predecessor to the KGB — recruited Hemingway. He may have agreed to work with them due to his anti-fascist beliefs. The writer was given the code name "Argo" and met with a Soviet handler in New York. Yet KGB files also note that Hemingway did not pass along useful information, despite "his willingness and desire to help us." By the end of the 1940s, he was no longer in contact with Soviet intelligence.

Hemingway also organized what he called a "Crook Factory" of informants in Cuba in the early 1940s. These individuals, many of whom were refugees from Spain's dictatorship, were supposed to gather intel on Nazi supporters in Cuba for Hemingway to pass to the U.S. ambassador. However, as with the Soviets, Hemingway didn't deliver helpful information. The Crook Factory's intelligence operation ceased in April 1943.

Ernest Hemingway, circa 1917

Ernest Hemingway, circa 1917

He had an outlandish plan to battle U-boats

During World War II, German U-boats often attacked U.S. ships in the Caribbean. From his home in Cuba, Hemingway formulated a plan to disable these submarines via his personal fishing boat, the Pilar. He thought that when the Pilar encountered a German vessel while on patrol, jai alai players who'd been added to the Pilar's crew could use their skills to fling grenades into the submarine hatches. Meanwhile, other crew members would machine gun the enemy boat.

Hemingway's plan, called Operation Friendless, received some support from the Office of Naval Intelligence, which aided in outfitting the Pilar with munitions, radio equipment and rebuilt engines. However, no amount of supplies could make Hemingway's fishing boat an equal opponent to a German sub — fortunately, the writer and his crew never met with a U-boat and his unique plan was not put to the test.

Much of his early work was lost at a train station

At Hemingway's request, in 1922 his first wife, Hadley Richardson, packed up almost every bit of her husband's writing — including carbon copies of his work — to bring to an editor. She took the suitcase holding these valuable contents to a Paris train station, where it went missing. Hemingway lost an in-progress novel, poems and short stories. The materials were never recovered.

READ MORE: The Many Wives of Ernest Hemingway

He protected James Joyce during fights

During his time in Paris in the 1920s, Hemingway and fellow writer James Joyce became drinking buddies. And if a dispute broke out when they were together, Joyce, who was less athletic and had bad eyesight, reportedly relied on Hemingway to defend him. In an interview years later, Hemingway described their shared adventures: "We'd go out, and Joyce would fall into an argument or a fight. He couldn't even see the man, so he'd say, 'Deal with him, Hemingway! Deal with him!'"

Ernest Hemingway's dog tags, WWII war correspondents credential, baby spoon, hunting bullets and compass

Ernest Hemingway's dog tags, WWII war correspondents credential, baby spoon, hunting bullets and compass

He led an expedition to 'liberate' the Ritz Hotel

In the summer of 1944, Hemingway was in France as a war correspondent covering the last days of World War II. He was also aware that German occupying forces had turned Paris' Ritz Hotel into their own headquarters. This didn't sit well with the writer, who'd developed a lasting fondness for the elite hotel since living in Paris in the 1920s.

On August 25, 1944, the day the Germans surrendered in Paris, Hemingway led a ragtag band of fighters that he'd dubbed his "Irregulars" and headed off to "liberate" the hotel from its occupying forces. Upon arrival, they learned that the Germans had already departed, but he made sure it wasn't a wasted trip. As was Hemingway's wont, he quickly hit the bar. There were reportedly more than 50 martinis on his tab by the time he was finished drinking that night.

He preferred to write while standing up

Hemingway usually wrote in the morning while standing in front of his desk and scribbling with a pencil. Though most of his work was in longhand, he did at times use a typewriter when he needed to get his thoughts down at a quicker pace, for example with dialogue. He said to The New Yorker, "When the people are talking, I can hardly write it fast enough or keep up with it." In his home in Cuba, Hemingway tallied each day's word count on a large cardboard chart; though he occasionally surpassed 1,000 words, his usual total was 400 to 700 words per day.

Ernest Hemingway at breakfast with a group of cats feeding at his feet, circa 1940s

Ernest Hemingway at breakfast with a group of cats feeding at his feet, circa 1940s

He was surveilled by the FBI

In his later years, Hemingway became extremely paranoid about being followed by the FBI. He told a friend that the feds had "bugged everything," were intercepting his mail and auditing his accounts. These beliefs were seen as a sign of Hemingway's mental decline — but the surveillance turned out to be true.

Thanks to the Freedom of Information Act, Hemingway's FBI file was made public after his death. It showed that the FBI had been tracking the writer since the 1940s when he was living in Cuba. The FBI kept an eye on Hemingway for the rest of his life. A friend came to believe that Hemingway's awareness of the FBI's monitoring may have contributed to his 1961 suicide.

He experienced multiple head injuries

Hemingway's life involved multiple head traumas. While in Italy during World War I, an explosion rendered him unconscious. He boxed, though he did insist that he "tried not to get hit." He got a concussion in a car crash in London in May 1944; instead of resting, he traveled to France as a war correspondent and in August received another head injury in a motorcycle accident. After the war, he fell on the deck of his boat and again concussed his head. In 1954, he was on a plane that went up in flames on an African runway; he ended up using his head to butt his way out of the fiery cabin.

It's possible that the above injuries resulted in Hemingway suffering from chronic traumatic encephalopathy. Though he had other psychiatric disorders, CTE could have contributed to his declining mental health at the end of his life.

One of his favorite meals was green turtle steak

While living in Florida's Key West, Hemingway enjoyed eating green turtle steak, a Keys delicacy. He liked the dish so much that when he was undergoing psychiatric treatment at the Mayo Clinic, a resident who'd become a friend had some of the steaks flown in from Florida so Hemingway could once again partake of a favorite meal.

READ MORE: Inside Ernest Hemingway's Key West Home and How It Inspired Many of His Famous Writings