Liddell Hart served as an officer in the British Army during World War I where he witnessed the horrors of a war led by incompetents. He set out in the following years to discover why the casualty rate had been so terribly high during the war, and arrived at a set of principles that he considered the basis of all good strategy, principles that, he claimed, were ignored by most commanders in World War I.
These principles can be reduced to a single phrase, the indirect approach, and two fundamentals:
In strategy the longest way round is often the shortest way there; a direct approach to the object exhausts the attacker and hardens the resistance by compression, whereas an indirect approach loosens the defender's hold by upsetting his balance.
He also claimed that
The profoundest truth of war is that the issue of battle is usually decided in the minds of the opposing commanders, not in the bodies of their meni.
This argues that one succeeds by keeping one's enemy uncertain about the situation and one's intentions, and by delivering what he does not expect and is therefore not prepared for.
He arrived at his conclusions after studying the great strategists of history and their victories. He believed the indirect approach was the common element in the men he studied. He also claimed the indirect approach was a valid strategy in other fields of endeavor, such as business, romance, etc.
Liddell Hart published his theories during the 1920s. They were well-received by many of the younger officers who would emerge as leaders in World War II. Paradoxically, Liddell Hart saw his theories successfully adopted by Germany and used against Britain and its allies. His theories were a central part of the German blitzkrieg tactics which were designed to hit the enemy so fast and so hard that he would not be able to establish or maintain an equillibrium. They were also openly endorsed by the German's most successful general, Erwin Rommel.
He was retired from the British Army as a Captain in 1927 and spent the rest of his career as a writer. He was initially a military analyst for various British newspapers. Later he began publishing military histories and biographies of great commanders who, he thought, were great because they illustrated the principles of good strategy. Among these were Scipio Africanus Major, William T. Sherman, and T.E. Lawrence. Shortly after World War II he interviewed/debriefed many of the highest ranking German generals and published their accounts as German Generals Talk.
The principal posthumous biography of Liddell Hart, Alex Danchev's Alchemist of War: The Life of Basil Liddell Hart, written with the cooperation of Liddell Hart's widow, is startling for its candor. Among its revelations are that Liddell Hart connived at the planting an endorsement of his own work in the English language version of Panzer Leader, the autobiography of Heinz Guderian. Although Guderian greatly admired Liddell Hart's work, and avidly read his newspaper columns, the German language edition of Guderian's autobiography gives Liddell Hart's work no greater preference than that of his contemporary, J.F.C. Fuller whom Guderian also admired.