After [Bill] Clinton and his advisors left office, they could only watch in alarm as Bush’s son, George W. Bush, took the keys to the NATO car and gunned it down that open road. Among other stops, the younger Bush attended the alliance’s summits in 2006 in Latvia, the first such event on former Soviet territory, and in 2008 in Bucharest, where he pushed hard for inclusion of Georgia and Ukraine. For Putin, that Bucharest summit—coming on top of Bush’s 2003 invasion of Iraq and his 2007 decision to erect ballistic missile defenses (in the form of ten ground-based interceptors in Poland and a radar facility in the Czech Republic), all around the time of “color revolutions” in post-Soviet states—proved to be the breaking point.
Sarotte, M. E.. Not One Inch (The Henry L. Stimson Lectures Series) (p. 348). Yale University Press. Kindle Edition (footnotes omitted)