This chapter examines how the theory and practice of war has evolved over the past two centuries. It first provides an overview of modern warfare and the transformation in the way that wars are fought. In particular, it charts the decline of limited warfare and considers the ideas of Prussian career soldier Carl von Clausewitz, along with the emergence of the Napoleonic way of war and the legacy of Napoleon Bonaparte with regard to strategy. It then discusses the impact of the Industrial Revolution on the planning for and conduct of war, focusing on the ways that weapons technology transformed both strategy and tactics. It also explores the evolution of naval warfare, how nuclear weapons ended the era of total war, and the rise of revolutionary warfare. Finally, it reflects on how the transition to postmodernity can influence war as a politico-cultural institution.