George Kennan (Diplomat, "Architect of the Cold War Containment Policy") - Criticized NATO expansion as a severe mistake in a 1998 interview with the New York T

George Kennan (Diplomat, "Architect of the Cold War Containment Policy") - Criticized NATO expansion as a severe mistake in a 1998 interview with the New York Times . Henry Kissinger (Former U.S. Secretary of State) - Expressed concerns about NATO expansion increasing tensions with Russia over several years, particularly noted in discussions and forums during the late 1990s and early 2000s. William Perry (Former U.S. Secretary of Defense) - Voiced apprehensions about the strategy and pace of NATO expansion, particularly in the late 1990s during his tenure and in reflections thereafter. Sam Nunn (Former U.S. Senator, Co-Chairman of the Nuclear Threat Initiative) - Warned of strategic miscalculations and heightened conflict risks due to expansion, prominently during the late 1990s and early 2000s. Jack Matlock (Former U.S. Ambassador to the Soviet Union) - Criticized NATO expansion for potentially setting the stage for conflict with Russia, in articles and public lectures, particularly during the 1990s.