In The Strategists, Professor Phillips Payson O'Brien shows how the views shaped by these five leaders in the First World War were crucial to understanding how they fought in the Second World War. For example, Churchill's experiences facing the German army in France in 1916 made him reluctant to commit large numbers of British soldiers there in the 1940s, while Hitler's mistakes on the Eastern Front were influenced by his reluctance to accept that circumstances had changed since his time. The effects of the power of leaders persist to this day: a true understanding of what is happening in Ukraine, for example, requires us to know what influenced the leaders involved. This is a history in which leaders—and their choices—matter, for better or worse.