George C. Wilson, shown here in Vietnam in 1968, died Feb. 11. He was 86. (The Washington Post)

George C. Wilson, an author and former Washington Post reporter who covered the military from the perspective of soldiers crawling in the mud and from the offices of decision-makers in Washington, and who played a notable role in the Pentagon Papers case, died Feb. 11 at his home in Arlington County. He was 86.

The cause was leukemia, said his son, Jim Wilson.

After working at Aviation Week and Space Technology magazine, Mr. Wilson joined The Post in 1966 as a military affairs reporter. He became a Pentagon “gold mine,” former Post executive editor Benjamin C. Bradlee wrote in his memoir.

Over the decades, Mr. Wilson examined how decisions were made about who would fight and when, where and with what equipment. He also was a Post correspondent in Vietnam in 1968 and 1972 and was the author of several books about military matters.

Mr. Wilson left The Post in 1990 and later wrote for National Journal, serving as an embedded correspondent in a mobile Marine artillery unit after the 2003 U.S. invasion of Iraq.

His books included “Supercarrier: An Inside Account of Life Aboard the World’s Most Powerful Ship, the USS John F. Kennedy” (1986), based on seven months of reporting on the $4 billion ship. He was on the vessel in 1983 when a terrorist bombing at the U.S. military compound in Beirut left 241 service members dead.

The Kennedy was ordered to carry out a retaliatory airstrike. A U.S. pilot subsequently died after ejecting from his plane, and another American flier was shot down over Lebanon and taken prisoner.

Writing in The Post, the naval historian Clark G. Reynolds called Mr. Wilson’s book “high drama, expertly told by a master observer” and “a brilliant social commentary on life at sea in the 1980s.”

Mr. Wilson’s next book, “Mud Soldiers: Life Inside the New American Army” (1989), told the dueling stories of an Army company that had sustained severe losses during the Vietnam War and a group of new trainees in the same company decades later.

The book was in many ways a critique of policies that lured new recruits from poor and troubled backgrounds for the all-volunteer force. “Mr. Wilson leaves no doubt that these young soldiers would fight and die if called on to do so,” reviewer Martin Kirby wrote in the New York Times. “But he also develops them as characters, appealing, sincere and unsophisticated, whose early deaths in battle would be unutterably tragic.”

The most dramatic moment of Mr. Wilson’s career may have come when he found himself in a federal courtroom, deep in the legal thickets of the Pentagon Papers case. The case, which arose in 1971, involved efforts to publish a trove of papers that formed a secret history of the Vietnam War and how the United States became embroiled in it.

After the papers were obtained by the New York Times and The Post, the Nixon administration tried to prevent the newspapers from publishing them, arguing that the revelations would damage national security. The government attempt to stop the publication of the secret papers was known as “prior restraint” and prompted questions about freedom of the press, guaranteed by the First Amendment.

In his memoir, Bradlee recounted a day in court in which the government extracted, from deep within the huge file of documents, a particular passage. If that passage were to be made public, the government told the judge, national security would be harmed.

Then, Bradlee wrote, “the remarkable George Wilson stunned everyone by pulling out of his back pocket a verbatim record” of the same information, which had already appeared in a public transcript of Senate Foreign Relations Committee hearings.

It was a turning point in the case and demonstrated Mr. Wilson’s encyclopedic knowledge of the most minute details of the war. It also showed him as a man who kept his wits in a tight spot.

The case ultimately went to the U.S. Supreme Court, which upheld the right of the newspapers to publish. The ruling has been viewed as vindication of the media and a triumph for believers in the First Amendment.

Many years later, Mr. Wilson described the immediate aftermath of his display of courtroom virtuosity. He said he was invited to ride back to The Post “in the company limo.” That mode of transport, he said, was “a first for this shiny-pants reporter.”

George Wilson Jr. was born July 11, 1927, in Orange, N.J. He took the middle name Cadman when he joined the Navy during World War II. He received a bachelor’s degree in English in 1949 from Bucknell University in Lewisburg, Pa.

Early in his career, he was a reporter for the Newark Evening News and Congressional Quarterly.

His wife of 50 years, the former Joan Gibbons, died in 2005. Survivors include two children, Kathy Wilson-Klatka of Riner, Va., and Jim Wilson of Arlington; a sister; and three grandchildren.

In 1990, Mr. Wilson wrote in The Post about a visit he made to Vietnam with a group of soldiers who had fought there. One former soldier, he said, found the tomb of a Vietnamese soldier born the same year he was.

On the grave of the dead Vietnamese, the American placed his Army Combat Infantryman Badge, Mr. Wilson wrote.

“Why did you do that?” he asked the soldier, who “got through his year in Vietnam unscathed.”

“He probably deserved it more than I do,” the soldier said. “Does that make sense?”

“I did not answer,” Mr. Wilson wrote. “As with so much else about the Vietnam War, I did not know whether it made sense or not.”