Sir Basil Henry Liddell Hart, commonly known throughout most of his career as Captain B. H. Liddell Hart, was a British soldier, military historian, and military theorist. He wrote a series of military histories that proved influential among strategists. Arguing that frontal assault was bound to fail at great cost in lives, as proven in World War I, he recommended the "indirect approach" and reliance on fast-moving armoured formations.

Military theory is the study of the theories which define, inform, guide and explain war and warfare. Military Theory analyses both normative behavioral phenomena and explanatory causal aspects to better understand war and how it is fought. It examines war and trends in warfare beyond simply describing events in military history. While military theories may employ the scientific method, theory differs from Military Science. Theory aims to explain the causes for military victory and produce guidance on how war should be waged and won, rather than developing universal, immutable laws which can bound the physical act of warfare or codifying empirical data, such as weapon effects, platform operating ranges, consumption rates and target information, to aid military planning.