By Danielle Rossingh, for CNN

(CNN) -- When a horse senses danger, its instincts tell it to run away as fast as possible.

But during the 1950-53 Korean War, one mare would run towards it: Staff Sergeant Reckless, the only horse in US history to have been promoted to the rank of sergeant.

Bought for $250 in 1952 by a US marine corps lieutenant at Seoul Race Track from a young Korean boy who needed the cash to buy his sister an artificial leg, the small horse would become America's greatest war horse.

Herd animal

Although she was bred as a racehorse, she was part Jeju, a local breed known for its hardiness. That toughness served her well when she became a pack animal trained to carry ammunition for the Anti-Tank Company of the 5th Marines in 1952.

The marines called her Reckless, after the recoilless rifle for which she carried ammunition. The cannon was often dubbed the "reckless" rifle because it was so dangerous to handle.

"Reckless was all alone when she joined the Marines," Robin Hutton wrote in her 2014 book "Sgt. Reckless. America's War Horse."

"Because horses are 'herd' animals, the Marines became her herd. She bonded so deeply with them that Reckless would go anywhere and do anything to help her adopted family."

Korean War battle

Reckless played an important role during the Battle of Outpost Vegas in the final stages of the Korean War between US and Chinese armed forces in March 1953.

During this five-day bloody battle, which is estimated to have cost the lives of 1,000 American and 2,000 Chinese soldiers, Reckless made 51 trips to resupply the guns with ammunition on one day alone.

All in all, the small mare carried 386 rounds of ammunition, weighing almost 4,000 kilograms, by walking more than 35 miles through rice paddies and steep mountain trails. After unloading the ammunition, Reckless would carry the wounded soldiers back down to safety, despite getting injured twice herself.

Astonishingly, Reckless did all of this mostly by herself whilst being under heavy enemy fire. She was trained to lie down when under fire and to avoid obstacles such as barbed wire.

'Lifeline'

"She was a critical lifeline to the guns that were firing in support of us," Sgt. Harold E. Wadley of the US Marine Corps, who served with Reckless during the Korean War, wrote in a foreword to Hutton's book.

At times, the Marines would use their own flak jackets to cover their comrade from incoming fire.

"Reckless was a very special horse and undoubtedly bonded through a spiritual connection of love with her Marines," said Wadley.

"The noise and waves of concussion can't be described, but she endured it all," said Wadley. "I believe an angel had to be riding Reckless, since she was alone and without a marine to lead her."

Beer, candy and coffee

Reckless, who would sleep in the soldiers' tents at night, also endeared herself to her fellow Marines in a different way.

"Reckless had a voracious appetite," Hutton, who is also president of the Sgt. Reckless Memorial Fund, wrote on a website dedicated to the horse. "She would eat anything and everything -- but especially scrambled eggs and pancakes in the morning with her morning cup of coffee.

"She also loved cake, Hershey bars, candy from the C rations, and Coca Cola -- even poker chips, blankets and hats when she was being ignored -- or if she was trying to just prove a point."

Reckless also enjoyed the occasional beer with her fellow Marines.

Hero's welcome

Reckless, whose military decorations included two Purple Hearts, received a hero's welcome when she was shipped from Korea to the US in 1954, with hundreds of people awaiting her arrival in San Francisco.

Having twice been promoted to staff sergeant, Reckless would spend the rest of her life at Camp Pendleton in California, where she gave birth to one filly and three colts, according to History.com.

Although her death in 1968 was front page news in the US, and she was buried with full military honors, the horse had become somewhat of a forgotten hero in the decades that followed.

Statues

But in recent years, the legend of Reckless has been resurrected, with a number of books being published and statues being unveiled at Virginia's National Museum of the Marine Corps and Heritage Center in 2013 and at Camp Pendleton in 2016.

Last weekend, on the 50th anniversary of her death in Camp Pendleton at the age of 20, a 1,000-pound bronze statue of Reckless was unveiled at Kentucky Horse Park in Lexington by four Korean War veterans—including Wadley, who served with her.

And perhaps fittingly given how she started life on a race track under the Korean name Flame of the Morning, her statue now stands alongside sculptures of racing legends Secretariat, winner of the 1973 Triple Crown, and 1920s champion Man o'War.

"Horse really run from chaos," Hutton told local Kentucky broacaster WHAS11. "But Reckless ran towards the chaos."