James R. Schlesinger, a Republican economist who advanced rapidly to some of the highest positions of government power in the 1970s but whose abrasive leadership style led to conflicts with presidents, bureaucrats and the American public, died March 27 at a hospital in Baltimore. He was 85.

The cause was complications from pneumonia, said his daughter Ann Schlesinger. He was an Arlington resident.

Mr. Schlesinger specialized in the economics of national security, which helped propel his rise during the Cold War from academia to influential jobs in the federal government, including CIA director, secretary of defense and the nation’s first secretary of energy.

He gained a reputation as someone willing to cut jobs and implement unpopular policies with little regard for what other people thought of him. In 1969, Mr. Schlesinger joined the Nixon White House staff as deputy director of the Bureau of the Budget, where he overcame Pentagon opposition to cut $6 billion from the defense budget during the Vietnam War. Impressed, Nixon named him chairman of the Atomic Energy Commission, which ran the nuclear weapons complex and regulated the nuclear power industry.

After Nixon won reelection in 1972, he effectively fired CIA Director Richard Helms after the two clashed over Helms’s refusal to impede the FBI investigation into the Watergate break-in, the botched political operation that ultimately led to the president’s resignation.

Nixon sent Helms to Iran as the U.S. ambassador and appointed the rugged-looking, pipe-smoking Mr. Schlesinger to lead the intelligence agency, which the president deeply distrusted. The president spoke resentfully of the Ivy Leaguers throughout the CIA and attributed to the agency a gentlemen’s club atmosphere that he found distasteful.

“Get rid of the clowns,” Nixon told Mr. Schlesinger, referring to the CIA’s staff. “What use are they? They’ve got 40,000 people over there reading newspapers.”

He took Nixon’s order to heart and in three months forced out 10 percent of the agency staff. When one subordinate said the mass firings appeared ruthless, Mr. Schlesinger responded: “Ruthless? I'm just trying to clear the aisle so I can walk.”

17 weeks at CIA

During Mr. Schlesinger’s 17-week tenure at the agency, information surfaced that the CIA had offered technical assistance for the September 1971 break-in at Daniel Ellsberg’s psychiatrist’s office.

A few years earlier, Ellsberg, a onetime defense analyst, had leaked to the New York Times a secret Pentagon history of the events leading to the Vietnam War.

Mr. Schlesinger was furious. He considered the break-in a violation of the CIA charter, which prohibits the agency from acting as a domestic secret police. He sent a memo to the CIA staff asking for information about any illegal activities the CIA had conducted since 1959. The responses revealed a history of illegal spying against Americans, including antiwar protesters and journalists. The CIA would uncover nearly 700 violations of its charter.

All the while, Nixon’s Cabinet was unraveling amid the Watergate affair. Nixon nominated Mr. Schlesinger as secretary of defense to replace Elliot Richardson, who was moving over to the Justice Department after the resignation of scandal-plagued Attorney General Richard Kleindienst.

When Mr. Schlesinger became defense secretary, in 1973, the U.S. troop presence in Vietnam was in the hundreds and declining.

His primary goal was to reform U.S. nuclear strategy, which relied on the threat of massive retaliation to annihilate the Soviet Union in the event of war.

Because the Soviet Union appeared to have achieved parity and the ability to respond to any U.S. attack, Mr. Schlesinger believed the old strategy was antiquated. He sought a more flexible policy that would prevent uncontrolled escalation by using limited strikes against military and industrial installations.

His views were deeply unpopular with Congress and with U.S. allies in Europe, who thought his proposal courted a nuclear exchange and made all-out war more likely. As part of a Cabinet shake-up, he was fired by President Gerald Ford in late 1975, before the policy was implemented.

Ford and Mr. Schlesinger never connected, and those around the president described Mr. Schlesinger as prone to lecturing Ford in a condescending way about military strategy.

Everything about Mr. Schlesinger seemed to annoy Ford, including Mr. Schlesinger’s disheveled attire. Ford took offense that he neither tightened his tie nor buttoned his collar before meeting with the president and often slung a leg over armchairs in the Oval Office.

“His aloof, frequently arrogant manner put me off,” Ford later told historian Walter Isaacson. “I could never be sure he was leveling with me.”

According to military historian Charles A. Stevenson’s 2006 history of the secretaries of defense, “SecDef,” Mr. Schlesinger “ultimately failed to keep his job because he never developed enough rapport, confidence, or support with people who could defend him when controversy arose.”

Timely switch to Carter

During the 1976 Republican primary, Mr. Schlesinger backed California Gov. Ronald Reagan’s challenge of Ford. After Ford won the nomination, Mr. Schlesinger switched his allegiance to the Democratic nominee, former Georgia governor Jimmy Carter.

Carter won and named Mr. Schlesinger his top energy policy adviser. When the Department of Energy was created in 1977, Carter appointed him secretary. Mr. Schlesinger set out to end natural gas price controls and reduce oil imports, and he argued for increased use of domestic coal and nuclear power to reduce the nation’s dependency on oil.

Mr. Schlesinger’s advocacy of nuclear power roiled environmental activists, especially after the 1979 partial core meltdown at the Three Mile Island nuclear power plant near Harrisburg, Pa.

Actress Jane Fonda and Gov. Jerry Brown (D-Calif.) sought Mr. Schlesinger’s dismissal, and they organized a Washington rally against his nuclear policies. Fonda told the crowd, estimated at 65,000 people, “Putting Schlesinger in charge of nuclear power is like putting Dracula in charge of a blood bank.” Brown was staging a primary campaign against Carter, and he planned to use the nuclear issue against the president.

Mr. Schlesinger, undeterred, derided the protesters as “the same people who were for Ho Chi Minh.”

Mr. Schlesinger helped draft a far-reaching energy reform bill in 1978 that ended natural gas price controls, offered a tax incentive for Americans to install solar panels on their homes and levied a tax on gas-guzzling vehicles.

It was a short-lived victory for the administration. Within months, the shah of Iran was deposed, and the subsequent Islamic regime halted oil exports to the United States. Gas prices soared, consumers panicked and drivers formed long lines at gas stations. Mr. Schlesinger sometimes seemed unsympathetic, and he blamed American driving habits for the problem.

Mr. Schlesinger became a symbol of the long gas lines that “marked the beginning of the end of the Presidency of Jimmy Carter,” wrote energy analyst Daniel Yergin in “The Prize,” his Pulitzer Prize-winning history of the American oil industry. Mr. Schlesinger left office in July 1979, part of a Cabinet reshuffling by Carter, whose poll numbers were sagging. At the time, Mr. Schlesinger said he was leaving the “onerous and miscellaneous responsibilities falling to the lot of the ‘energy czar.’ ”

Elite education

James Rodney Schlesinger was born Feb. 15, 1929, in New York City, where he graduated from the exclusive Horace Mann School. He received a bachelor’s degree in economics from Harvard University in 1950 and a master’s degree and doctorate in economics from Harvard in 1952 and 1956, respectively.

Raised in a middle-class Jewish family, he converted to the Lutheran faith after a visit to Germany in 1950. He was often described as Calvinist in his tastes. He shunned creature comforts and preferred the study of Lutheran theology to attending Georgetown cocktail parties.

While pursuing his graduate studies, he married Rachel Mellinger, who was studying at Radcliffe. She died of cancer in 1995. Survivors include eight children, Cora Schlesinger of Richmond, Charles Schlesinger of Benbrook, Tex., James Schlesinger Jr. of Front Royal, Va., and Ann Schlesinger, William Schlesinger, Emily Schlesinger, Thomas Schlesinger and Clara Schlesinger, all of Arlington; and 11 grandchildren.

After completing his doctorate, Mr. Schlesinger became a professor of defense economics at the University of Virginia. He later taught at the Naval War College in Rhode Island, and his lectures there were anthologized in a book, “The Political Economy of National Security” (1960).

The book caught the attention of the Rand Corp., a Santa Monica, Calif.-based think tank that often advised the government. He became a specialist on nuclear issues for Rand in 1963 and consulted with the White House on federal budget issues.

After leaving the Department of Energy, Mr. Schlesinger worked as a consultant for Lehman Bros., a New York investment bank, and for many years, he was chairman of the Mitre Corp., a nonprofit government research group. He remained involved until shortly before his death with national security affairs.

Reflecting on his career, Mr. Schlesinger told historian Isaacson that he had mellowed. “I tended to be too self-righteous, a quibbler, stubborn, too,” he said. “It took me a while to understand how hard I must have been to deal with.”