Kennedy examines how military strategy evolved from the Franco-Prussian War to World War II. He highlights the shifts in strategic thinking, the impact of technological advancements, and the changing nature of warfare. This theme underscores the importance of adapting military strategies to meet new challenges and the consequences of failing to do so.

The book emphasizes the critical role of diplomacy in preventing and resolving conflicts. Through detailed case studies, Kennedy illustrates how diplomatic efforts, negotiations, and alliances were pivotal in shaping the outcomes of major conflicts. This theme highlights the delicate balance between military power and diplomatic finesse in achieving national objectives.

Kennedy delves into the contributions of influential leaders and strategists who played pivotal roles during this period. By examining the decisions and actions of figures such as Bismarck, Churchill, and Roosevelt, the book provides valuable insights into how individual leadership and vision can significantly impact the course of history. This theme underscores the importance of strong leadership in navigating complex geopolitical landscapes.