George Kennan: A key architect of the U.S. Cold War containment policy, Kennan warned in a 1998 New York Times interview that NATO’s eastward expansion was “the beginning of a new cold war.” He predicted that it would provoke an adverse Russian reaction, inflaming tensions and affecting Moscow’s policies. He later called it a “fateful error” in a 1997 op-ed, arguing it would destabilize European security.
Henry Kissinger: A former U.S. Secretary of State and influential realist thinker, Kissinger cautioned against NATO expansion that included Ukraine. In a 2014 Washington Post piece, he argued that pushing Ukraine into NATO would be perceived by Russia as a strategic threat, risking escalation and conflict.
Noam Chomsky: A prominent linguist and political commentator, Chomsky has long criticized NATO expansion as a provocative move against Russia. He argued that integrating former Soviet states like Ukraine into NATO would predictably lead to Russian backlash, including military action, as it threatened Moscow’s sphere of influence.
John Mearsheimer: A leading international relations scholar and proponent of realist theory, Mearsheimer warned in a 2014 Foreign Affairs article that NATO expansion, particularly into Ukraine and Georgia, was a key driver of the Ukraine crisis. He predicted that it would lead Russia to take drastic measures, including war, to prevent Western encroachment.
Stephen F. Cohen: A renowned historian and expert on Russian studies, Cohen argued in 2014 that moving NATO closer to Russia’s borders would militarize the situation. He viewed it as an existential threat to Russia, predicting that Moscow would not back down, leading to prolonged conflict.
Samuel Huntington: The political scientist known for "The Clash of Civilizations" warned that expanding NATO into Eastern Europe, especially near Russia’s borders, would heighten tensions. He saw it as risking a broader confrontation by crossing cultural and geopolitical fault lines.
Jack Matlock: A former U.S. Ambassador to the Soviet Union, Matlock was among the 50 prominent experts who signed a 1997 open letter to President Clinton opposing NATO expansion. He argued that it would destabilize European security and provoke Russia, a prediction borne out by later events.
Robert McNamara: The former U.S. Secretary of Defense joined the same 1997 letter, cautioning that NATO enlargement would decrease allied security and unsettle European stability, potentially leading to Russian aggression.
Richard Pipes: A historian and anti-Soviet hawk, Pipes also signed the 1997 letter. Despite his hardline stance on the Soviet Union, he warned that NATO’s eastward push would unnecessarily antagonize Russia, risking conflict.
William Perry: A former U.S. Secretary of Defense, Perry nearly resigned in 1994 over NATO expansion plans. He later wrote in his memoir that the decision to expand NATO was a mistake that would alienate Russia and lead to confrontation, a view he reiterated in later years.
Ted Galen Carpenter: A foreign policy analyst and realist, Carpenter wrote in The Guardian in 2022 that NATO expansion was a tragic mistake. He argued that warnings from analysts like himself about inevitable Russian pushback had been ignored for over 25 years.
Jeffrey Sachs: An economist and public policy scholar, Sachs has argued that NATO expansion was a primary cause of the Ukraine crisis. He predicted that it would lead to war, a view he has maintained since the 1990s, though he faced criticism for it after 2022.
