Marine Corps Capt. Arthur J. Jackson, who received the Medal of Honor for killing 50 Japanese soldiers and silencing a dozen enemy pillboxes during the World War II battle of Peleliu, and almost two decades later was forced out of the service after covering up his slaying of an alleged Cuban spy, died Wednesday in Boise, Idaho. He was 92.

The Congressional Medal of Honor Society announced the death but did not provide a cause.

Jackson, then 19, was with the 1st Marine Division in the western Pacific during one of the most grueling battles in that theater of operations. He was among the wave of U.S. forces that landed on Japanese-controlled Peleliu on Sept. 15, 1944, with the intent of overtaking it within days and securing the entire Palau Islands chain in advance of the invasion of the Philippines and Japan.

Instead they met a large, determined and heavily fortified Japanese resistance, about 11,000 troops in all, that inflicted heavy casualties and kept the battle raging for two months before U.S. forces prevailed. Eventually more than 27,000 Americans were involved in the struggle for Peleliu, and they endured one of the highest rates of death and injury in the Pacific, with at least 2,300 killed and 8,400 wounded.

Jackson’s unit was ordered to clear the southern end of the island, but on Sept. 18, they were stalled by a storm of enemy gunfire coming from a large Japanese bunker. He was told to move ahead alone and clear it.

Loaded up with grenades, he charged the pillbox, raking it with automatic fire while discharging white phosphorus grenades and other explosives. He was credited with killing all 35 occupants.

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Continuing alone and again at tremendous peril, he repeated the same maneuver at 11 smaller pillboxes that contained another 15 Japanese soldiers.

“Stouthearted and indomitable despite the terrific odds, Jackson resolutely maintained control of the platoon’s left flank movement throughout his valiant one-man assault and, by his cool decision and relentless fighting spirit during a critical situation, contributed essentially to the complete annihilation of the enemy in the southern sector of the island,” read his citation for the Medal of Honor, the military’s highest award for valor.

He was wounded both at Peleliu and subsequently at Okinawa, receiving two Purple Hearts. In October 1945, President Harry S. Truman bestowed the medal on then-2nd Lt. Jackson at a White House ceremony. He met with dignitaries including Adm. Chester W. Nimitz and Gen. James H. Doolittle. He was feted in a Manhattan ticker-tape parade, riding in a car with columnist Walter Winchell.

Four years later, he joined the Army as a commissioned officer. But after a decade, he returned to the Marines and was serving as a company commander at Guantánamo Bay on Sept. 30, 1961 — during the unnerving interim between the disastrous Bay of Pigs invasion and the Cuban missile crisis.

On that night, then-Capt. Jackson said he was alarmed to find a 44-year-old Cuban, Ruben Lopez, in a restricted part of the base used for ammunition storage. Lopez worked as a bus driver on the site, even though he expressed openly pro-Fidel Castro sympathies and was under surveillance by naval intelligence.

On his own initiative, Capt. Jackson decided to eject Lopez with the help of his executive officer, Marine 1st Lt. William Szili. They said they marched him to a long-unused rear gate, but they found the lock rusted shut. Capt. Jackson said he sent Szili to get something to break the lock and, while left alone, Lopez leapt at him. He shot the Cuban with his sidearm.

With the assistance of a few other Marines, Capt. Jackson buried Lopez in a shallow grave on the base.

Szili described an atmosphere of heavy drinking on the base — he said he had been with Capt. Jackson at an officers’ bar on the night of the killing — and that word of the death leaked during one cocktail party.

After the body was discovered, the Defense Department issued a terse statement noting an investigation was underway. The story gained no traction, but Capt. Jackson quietly left the military in March 1962 after being denied a court-martial (and the publicity it could generate) to clear his name.

The full tale came to light in April 1963, when Capt. Jackson was poised to appear at a White House event with President John F. Kennedy honoring Medal of Honor recipients. Szili said he had been discharged by that time — under threat of a $10,000 fine and 10 years in prison if he disclosed the killing — and he was seeking reinstatement.

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The Philadelphia Bulletin and the syndicated columnist Jack Anderson reported the cover-up, a Cold War blockbuster that had the potential to become an international incident. Capt. Jackson, then working as a $90-a-week letter carrier in San Jose, sent his regrets to the White House.

He stayed mum, but his wife spoke to the San Jose Mercury News to say her husband had been “thrown out” of the corps and pressed into signing a statement forbidding discussion of the incident, lest he face the same fine and imprisonment as Szili. He left 18 months before he was eligible for a full pension.

He later worked in a warehouse and managed a pizza parlor before joining the Veterans Administration and retiring as chief of veterans services for Idaho.

Arthur Junior Jackson was born in Cleveland on Oct. 18, 1924, and grew up in Canton, Ohio, and later Portland, Ore., moving for his father’s job as a watchmaker during the Depression.

He was a high school athlete, lettering in baseball, football and track. After graduation, he left for a construction job in Alaska, helping build a runway at a naval air station near Sitka. After enlisting in the Marine Corps as an infantryman, he distinguished himself during the New Britain campaign in the Pacific in late 1943.

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His first marriage, to the former Dolores Bawden, ended in divorce. Survivors include his wife, Kathlyn Doell Jackson of Boise; five children from his first marriage, A.J. Jackson of Ashland, Ore., Kathy Watson of Rhinelander, Wis., Susan Claycomb of Lakewood, Colo., Lori Hickerson of Littleton, Colo., and Monte Jackson of Boise; seven grandchildren; and seven great-grandsons.

Capt. Jackson, who said he long felt “ashamed” of his Guantánamo killing, did not speak publicly about the incident until an Idaho Statesman reporter interviewed him in 2013.

He said his key concern was his “understanding” of a treaty between the United States and Cuba that could have resulted in his detention in a notorious Cuban prison.

“I hoped no one would find out,” he told the newspaper. “The world found out.”