Joseph Nye, who has died aged 88, owed his fame in the diplomatic world to just two words: “soft power”. The international affairs scholar came up with the phrase while sitting at his kitchen table trying to find a way to condense and encapsulate his approach to US foreign policy.

He acknowledged military force and economic power were essential components in pursuit of the national interest but argued there was a third element, one not requiring force, that was under-appreciated. He called it soft power: influence gained through aid, culture, news and agencies promoting human rights, democracy and freedom of speech.

The term gained currency from the 1990s onwards, not just in US policy circles but in foreign ministries around the world, including the UK and China. “I wish I had a nickel for every time it’s used,” he said in an interview with the Harvard Gazette in 2017.

Nye’s approach to foreign policy was the complete antithesis of Donald Trump’s. Normally mild-mannered and moderate, he was outspoken in his criticism of Trump, watching in dismay in the final months of his life as the American president undercut institutions that Nye regarded as essential to soft power, among them USAID (United States Agency for International Development), Voice of America, cultural programmes, and universities.

He spent most of his career in academia, where he was dean of Harvard’s Kennedy School of Government from 1995 to 2004. He also served in the state department and the Pentagon under presidents Jimmy Carter and Bill Clinton, and his thinking had a huge impact on the administration of Barack Obama.

Nye first came to prominence in 1977 when he co-authored Power and Interdependence: World Politics in Transition with a Harvard colleague, Robert Keohane, which was to become a standard text for students in the following four decades. Writing in the aftermath of the Vietnam war, they argued that military power could become a declining force in a world in which there was increased economic cooperation and the growing importance of multilateral organisations such as the UN.

Nye came up with soft power – as opposed to military and economic hard power – in response to the British historian Paul Kennedy’s 1987 book The Rise and Fall of the Great Powers, which warned of US decline because of its over-emphasis on military spending. Nye countered this with Bound to Lead: The Changing Nature of American Power, published in 1990. He disputed that the US was in decline and argued it could retain influence through pursuit of soft power. He developed the concept more fully in Soft Power: The Means to Success in World Politics (2004).

In an interview in 2008 with the digital magazine Guernica he said: “I noticed that the way we think about power is often related to tangible resources. People would say if you have a lot of tanks, you have power; or if you have a big economy, you have power. It struck me that there was something intangible – ideas, values – and it struck me that humans are moved by ideas and values, and it may not be tangible or hard, but it’s still a form of power and that led me to the idea of soft power.”

Critics of the concept argue it is too fuzzy and its impact limited. The historian Niall Ferguson, in an article in Foreign Policy magazine in 2003, wrote: “But the trouble with soft power is that it’s, well, soft. All over the Islamic world kids enjoy (or would like to enjoy) bottles of Coke, Big Macs, CDs by Britney Spears and DVDs starring Tom Cruise. Do any of these things make them love the United States more? Strangely not.”

Nye expanded on soft power as co-author in 2007 of the report A Smarter, More Secure America. He argued in favour of “smart power”, in which leaders, instead of over-reliance on military power, would choose from a myriad of hard and soft options depending on the issue. The phrase smart power originated in an article in Foreign Affairs magazine in 2004 by Suzanne Nosell, a human rights advocate and analyst, and Nye developed and popularised it.

Nye served under Carter as deputy under-secretary in the state department from 1977 to 1979 and chaired the national security council group on the nonproliferation of nuclear weapons. He served under Clinton as chair of the national intelligence council at the state department and in 1994-95 worked at the Pentagon as assistant secretary for defence for international security affairs.

The Chinese president Xi Jinping and his predecessor Hu Jintao both expressed an interest in pursuing a soft power strategy, and in 2007 Nye was invited to a private dinner in Beijing to discuss his ideas. Nye was sceptical, given China’s human rights record, and initially said China was using the term in a way he had not originally intended. But in an article written weeks before his death, for the magazine Monocle, he said that China valued soft power and stood ready to fill the vacuum that Trump was creating.

Born in South Orange, New Jersey, Joseph was the son of Else (nee Ashwell), who had been a secretary, and Joseph Sr, a partner in a Wall Street trading firm. Joseph Jr went to Morristown Beard school in New Jersey, then Princeton University, where he graduated with a BA in economics, history and politics in 1958. He followed this with two years at Exeter College, Oxford, as a Rhodes scholar studying philosophy, politics and economics.

On completing a PhD at Harvard in 1964, he joined the faculty there. He recalled the 1970s as a time of turbulence because of civil rights and Vietnam protests and a bomb going off in his office building.

He was a visiting fellow at the Royal Institute of International Affairs in London (1974), a visiting scholar at St Anthony’s College, Oxford, (1989) and a visiting professor at Balliol College, Oxford (2005).

Nye married Mary – known as Molly – Harding, whom he had known since they were teenagers, in 1961, and they settled in Lexington, Massachusetts, where she ran an art gallery.

Molly died in 2024. He is survived by three sons, John, Ben and Dan, and nine grandchildren.

• Joseph Samuel Nye, political scientist and US government official, born 19 January 1937; died 6 May 2025