NATO’s uncompromising promise to admit Ukraine to the alliance was the casus belli that the Russian Federation has maintained in justification of its invasion of Ukraine in February 2022. How important was the NATO factor in sparking the biggest war in Europe since the Second World War? In his latest book, Jonathan Haslam, one of the world’s greatest experts on Russian foreign policy and espionage, traces the origins of the Russo-Ukrainian War through a sequence of events to the early 1990s that lead us not to Russia or Ukraine, but to the other side of the Atlantic.