Like his predecessor Henry A. Kissinger, Mr. Brzezinski was a foreign-born scholar (he in Poland, Mr. Kissinger in Germany) with considerable influence in global affairs, both before and long after his official tour of duty in the White House. In essays, interviews and television appearances over the decades, he cast a sharp eye on six successive administrations, including that of Donald J. Trump, whose election he did not support and whose foreign policy, he found, lacked coherence.

Mr. Brzezinski was nominally a Democrat, with views that led him to speak out, for example, against the “greed,” as he put it, of an American system that compounded inequality. He was one of the few foreign policy experts to warn against the invasion of Iraq in 2003.

But in at least one respect — his rigid hatred of the Soviet Union — he had stood to the right of many Republicans, including Mr. Kissing

He supported billions in military aid for Islamic militants fighting invading Soviet troops in Afghanistan. He tacitly encouraged China to continue backing the murderous regime of Pol Pot in Cambodia, lest the Soviet-backed Vietnamese take over that country.

He managed to delay implementation of the SALT II arms treaty in 1979 by raising objections to Soviet behavior in Vietnam, Africa and Cuba; and when the Soviets went into Afghanistan late that year, “SALT disappeared from the U.S.-Soviet agenda,” as he noted in a memoir four years later.

Mr. Brzezinski, a descendant of Polish aristocrats (his name is pronounced Z-BIG-nyehv breh-ZHIHN-skee), was a severe, even intimidating figure, with penetrating eyes and a strong Polish accent. Washington quickly learned that he had sharp elbows as well. He was adept at seizing the spotlight and freezing out the official spokesman on foreign policy, Secretary of State Cyrus R. Vance, provoking conflicts that ultimately led to Mr. Vance’s resignation.

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Where Mr. Vance had endorsed the Nixon-Kissinger policy of a “triangular” power balance among the United States, China and the Soviet Union, Mr. Brzezinski scorned such “acrobatics,” as he called them. He advocated instead what he called a deliberate “strategic deterioration” in relations with Moscow, and closer ties to China.

Moving Fast

By his own account, he blitzed Mr. Carter with memos until he got permission to go to Beijing in May 1978, over State Department resistance, to begin talks that would lead to full diplomatic relations seven months later. Immediately after the trip, he appeared on “Meet the Press,” unleashing a slashing attack on the Soviet Union that Mr. Vance deplored as “loose talk.”

Mr. Brzezinski was also a prime mover behind the commando mission sent to rescue the American hostages held by Ayatollah Ruhollah Khomeini’s revolutionary forces in Iran after the overthrow of the shah of Iran, Mohammed Reza Pahlavi — a disastrous desert expedition in April 1980 that claimed eight lives and never reached Tehran. Mr. Vance had not been informed of the mission until a few days before. It was the final straw: He quit, “stunned and angry,” he said.

Mr. Brzezinski’s rationale for the rescue attempt was, perhaps inevitably, rooted in his preoccupation with Soviet influence. He contended that trying to gain the release of the hostages through sanctions and other diplomatic measures “would deliver Iran to the Soviets,” although many thought that outcome highly improbable, given the fundamentalism of the clerics running the country. Besides, he said, success would “give the United States a shot in the arm, which it has badly needed for 20 years,” a reference to the quagmire of the Vietnam War.

Soviet aggression in Asia, the Middle East, Africa and Latin America was by no means a figment of Mr. Brzezinki’s imagination. But his strict adherence to ideas in which virtually every issue circled back to the threat of Soviet domination was remarkable even for those tense times, when many in the foreign policy establishment had come to regard détente — a general easing of the geopolitical tensions between the Soviet Union and the United States — as the best course.

In his scholarly certitude, Mr. Brzezinski sometimes showed a tendency to believe that any disagreement between theory and reality indicated some fault on the part of reality. In his 1962 book “Ideology and Power in Soviet Politics,” for example, he asserted that the Communist bloc “is not splitting and is not likely to split” just as Beijing and Moscow were breaking apart.

With the breakup of the Soviet Union, Mr. Brzezinski allowed that it would make sense for the United States to engage with Russia, though cautiously, as well as China, “to support global stability.” And although he condemned Russian meddling in elections in the United States and elsewhere, he thought the effects were only marginal relative to the underlying problems shaking up Western societies.

In any case, aside from his ideological principles, he had both personal and historical reasons for abhorring the Soviet system.

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A Soviet Refugee

Zbigniew Kazimierz Brzezinski was born in Warsaw on March 28, 1928. His father, Tadeusz, was a diplomat who took the family along to France, then to Germany during the rise of Hitler in the 1930s and, fortuitously, to Canada on the eve of World War II. When the Russians took over Poland at the end of the war, Tadeusz Brzezinski chose to retire in Canada rather than return home.

The younger Mr. Brzezinski graduated from McGill University in Montreal in 1949 and earned a master’s degree there in 1950. Then it was on to Harvard, which granted him a doctorate in political science in 1953 and appointed him as an instructor. He and Mr. Kissinger were among the candidates for a faculty position; when Mr. Kissinger won an associate professorship in 1959, Mr. Brzezinski decamped to Columbia University.

He was not always consistent in his positions as he moved between one situation and another. When he was appointed to the State Department’s Policy Planning Council in 1966, he had already become an outspoken defender of United States engagement in the Vietnam conflict.

In 1968, after riotous antiwar protests at Columbia and elsewhere, he wrote in The New Republic that students should not be allowed to “rally again under the same leadership,” meaning they should be tried and incarcerated.

“If that leadership cannot be physically liquidated, it can at least be expelled from the country,” he wrote.

That same year, however, he resigned from the State Department planning council as a protest against expanded American involvement in the war in Indochina under President Lyndon B. Johnson.

Then he became a foreign policy adviser to Vice President Hubert H. Humphrey, who defended the expansion in his 1968 presidential campaign.

His bond with Jimmy Carter developed through the Trilateral Commission, the group David Rockefeller created in 1973 as a forum for political and business leaders from North America, Western Europe and Japan to consider the challenges facing industrialized countries. Mr. Brzezinski was the commission’s first director. (Mr. Rockefeller died in March.)

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In 1974, Mr. Brzezinski invited Mr. Carter, then the governor of Georgia and a rising Democratic star, to become a member. Two years later, Mr. Carter was the Democratic nominee for president, and he hired Mr. Brzezinski as a foreign affairs adviser.

Vying for Influence

From the start of his tenure as Mr. Carter’s national security adviser, Mr. Brzezinski jockeyed for power. He reserved for himself the right to give Mr. Carter his daily intelligence briefing, which had previously been the prerogative of the Central Intelligence Agency. He frequently called journalists to his office for what he called “exclusive” not-for-attribution briefings in which he would put his own spin on events, to the annoyance of Mr. Vance.

And although he was familiarly called Zbig and could be very engaging, he was quick to smack down reporters who dared to challenge his ideas. “I just cut off your head,” he told a journalist after one such retort.

A prolific author, Mr. Brzezinski published a memoir in 1983 about his White House years, “Power and Principle,” in which he recalled a range of policy objectives that went beyond containing the Soviets. “First,” he wrote, “I thought it was important to try to increase America’s ideological impact on the world” — to make it again the “carrier of human hope, the wave of the future.”

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He also said that he had aimed to restore America’s appeal in the developing world through better economic relations, but acknowledged that he had concentrated too much of his attention on those countries that he felt were threatened by Soviet or Cuban takeovers.

More recently, in opposing the invasion of Iraq, he predicted that “an America that decides to act essentially on its own” could “find itself quite alone in having to cope with the costs and burdens of the war’s aftermath, not to mention widespread and rising hostility abroad.”

In “Second Chance: Three Presidents and the Crisis of American Superpower,” published in 2007, he assessed the consequences of that war and criticized the successive administrations of George Bush, Bill Clinton and George W. Bush for failing to take advantage of the possibilities for American leadership from the time the Berlin Wall came down in 1989. He considered George W. Bush’s record, especially, “catastrophic.” And in the 2008 presidential campaign, he wholeheartedly supported Barack Obama.

Four years later, he once again assessed the United States’ global standing in “Strategic Vision: America and the Crisis of Global Power.” Here he argued that continued American strength abroad was vital to global stability, but that it would depend on the country’s ability to foster “social consensus and democratic stability” at home.

Essential to those goals, he wrote, would be a narrowing of the yawning income gap between the wealthiest and the rest, a restructuring of the financial system so that it no longer mainly benefited “greedy Wall Street speculators” and a meaningful response to climate change.

A United States in decline, he said — one “unwilling or unable to protect states it once considered, for national interest and/or doctrinal reasons, worthy of its engagement” — could lead to a “protracted phase of rather inconclusive and somewhat chaotic realignments of both global and regional power, with no grand winners and many more losers.”

Mr. Brzezinski, who had homes in Washington and Northeast Harbor, Me., was married to the Czech-American sculptor Emilie Benes, with whom he had two children in addition to Ms. Brzezinski: Mark Brzezinski, a lawyer and former ambassador to Sweden under President Barack Obama, and Ian Brzezinski, whose career has included serving as a deputy assistant secretary of defense. All survive him. He is also survived by a brother, Lech, and five grandchildren.

Into his 80s Mr. Brzezinski was still fully active as a teacher, author and consultant: a professor of foreign policy at Johns Hopkins University’s School of Advanced International Studies, a scholar at the Center for Strategic and International Studies, and a frequent expert commentator on PBS and ABC News.

He was, in short, a man who could be counted on to have strong opinions, and a boundless eagerness to share them. Once, in 1994, he even put forward a sort of disarmament program to solve the problem of breaking ties in the final game of the soccer World Cup.

“In the event of a tie,” he wrote to the sports editor of The Times, “the game should be resumed as a sudden-death overtime, but played with only nine players on each side, with each team compelled to remove two of its defensive players. That change increases the probability of a score and places more emphasis on offensive play. If after 10 minutes of play there is still no score, the game continues with four defenders removed from each team.”