Jonathan Schell is flanked by historian Stephen B. Oates and Ethel Kennedy at a gathering in McLean, Va., in 1983. (Larry Morris/The Washington Post)

Jonathan Schell, who as a 24-year-old graduate student visiting Vietnam wrote a memorably lacerating account of American involvement in the war and whose later publications included “The Fate of the Earth,” a best-selling volume that helped propel the nuclear freeze movement of the 1980s, died March 25 at his home in Brooklyn. He was 70.

He had leukemia and skin cancer, said his companion, ­Irena Gross.

Mr. Schell came from a prominent family of lawyers, writers and activists. His father, Orville H. Schell Jr., was a Wall Street lawyer and arts patron and also chaired the human rights group Americas Watch. His older brother, also named Orville, is a noted author and China scholar.

In a two-decade career as a New Yorker staff writer that started in the late 1960s, Jonathan Schell was regarded as an observant, circumspect war correspondent and political journalist. His tone was one of polished skepticism but at times bled into more-impassioned analysis.

“No doubt people have a natural tendency to try to forget about wars the minute they are over,” he commented wryly of the Vietnam War in 1971, “but we may be the first country to try to forget about a war while it is still going on.”

The war was transformative for Mr. Schell, in his private life and his career.

He had left Harvard in 1965 with a degree in Far Eastern history and, after studying Japanese at the International Christian University in Tokyo, stopped in Vietnam in January 1967 while on his way home.

American involvement in the war was at its peak, with hundreds of thousands of U.S. soldiers deployed. Mr. Schell saw them as unprepared for the task and growing wantonly resentful against a population “they were supposed to be saving but who didn’t want to be saved.”

With credentials as a journalist for the Harvard Crimson newspaper, he managed to board a helicopter that participated in an assault on an area considered a Communist redoubt. The village of Ben Suc was destroyed in the process.

Mr. Schell’s account of the mission was relentlessly grim, with descriptions of the killing of villagers and even farm animals.

Back in the United States, Mr. Schell submitted a story about Ben Suc to New Yorker editor William Shawn, whose son Wallace had been a friend since boarding school. “The Village of Ben Suc” also appeared in book form in 1967, earning praise as one of the most disturbing works about the war.

In his New York Times review of the book version of “The Village of Ben Suc,” author and diplomat John Mecklin called it “eloquently sensitive, subtly clothed in an aura of detachment, understated, extraordinarily persuasive.”

In subsequent visits to Vietnam, Mr. Schell wrote scalding critiques of U.S. military strategy.

As American troops were slowly withdrawn in the early 1970s, the U.S. armed forces continued massive bombing runs by air in Vietnam and Cambodia. “Never has a nation unleashed so much violence with so little risk to itself,” Mr. Schell wrote. “It is the government’s way of waging war without the support of its own people, and involves us all in the dishonor of killing in a cause we are no longer willing to die for.”

As an outgrowth of his war writing, Mr. Schell published essays on the Nixon administration and the fallout of the Watergate scandal, which led to the president’s resignation in 1974. Mr. Schell won the prestigious George Polk Award in 1976 for his essays about a betrayal of trust he saw prevalent at all levels in society, filtering down from the Oval Office.

After the publication of “The Time of Illusion,” his 1976 book about the Nixon era, Mr. Schell spent five years researching and writing what would become his best-known and most controversial work, “The Fate of the Earth.”

The book, excerpts of which first ran in the New Yorker, described the consequences of a full-scale nuclear exchange. In addition to the annihilation of humans as a species, “The Fate of the Earth” also ruminated on the metaphysical dimensions of extinction — the end of love, politics and art.

The book concluded with the view that the Cold War rationale behind deterrence — massive retaliation by the Americans or the Soviets — was not a necessary evil but a “monumental logical mistake.”

“One cannot credibly deter a first strike with a second strike whose raison d’etre dissolves the moment the first strike arrives,” Mr. Schell wrote.

CBS newsman Walter Cronkite called the book “one of the most important works of recent years,” which helped propel “The Fate of the Earth” to commercial heights seldom reached by jargon-laden tomes on nuclear disarmament.

“Fate” also had strong critics. Physicist Edward Teller, the “father” of the hydrogen bomb, denounced the book as “a singularly successful piece of terror-inspiring distortion” and “just another means to avoid coming to grips with imperfect solutions.”

The controversy only brought Mr. Schell more attention during a peak moment of the nuclear-freeze movement. In 1982, the same year the book came out, hundreds of thousands of demonstrators filled New York’s Central Park to protest the nuclear arms race.

The cause of ending the nuclear arms race defined much of Mr. Schell’s later writings, in such books as “The Abolition” (1984) and “The Seventh Decade: The New Shape of Nuclear Danger” (2007). He also lectured at Yale University on nonviolence and nuclear issues and, in recent years, was working on a book about climate change.

Jonathan Edward Schell was born Aug. 21, 1943, in New York City. He graduated in 1961 from the private Putney School in Vermont and in 1965 from Harvard.

During his tenure at the New Yorker, Mr. Schell was groomed as a possible successor to Shawn, but Mr Schell resigned in 1987 when Shawn was let go by publisher S.I. Newhouse Jr. Mr. Schell became a current-affairs columnist at Newsday and, in later years, became a correspondent for the Nation magazine.

Besides his companion, survivors include his wife, the former Elspeth Fraser, both of Brooklyn; three children from his marriage, Matthew Schell, Phoebe Schell and Thomas Schell, all of Brooklyn; his brother, Orville Schell of Bolinas, Calif.; a sister, Suzanne Pearce of Cambridge, Mass.; three half-brothers; and two grandsons.

At times, Mr. Schell’s critics pointed out that his books raised important questions about man’s ability to destroy itself but seldom offered concrete solutions.

“No single person can possess the wisdom to chart our course,” he wrote in “The Abolition. “It is in the very nature of things that the effort will be collective. The world is not to be approached, blueprint in hand, as if it were so much raw material waiting to be fashioned to someone’s design.”