Trench warfare
Trench warfare occurred when a revolution in firepower was not matched by similar advances in mobility, resulting in a grueling form of warfare in which the defender held the advantage. On the Western Front in 1914–1918, both sides constructed elaborate trench, underground, and dugout systems opposing each other along a front, protected from assault by barbed wire, mines, camouflaged trapping pits, and other obstacles. The area between opposing trench lines (known as "no man's land") was fully exposed to artillery fire from both sides. Attacks, even if successful, often sustained severe casualties.
Experimental Mechanized Force
In the aftermath of the First World War, several theorists sought ways to avoid a repetition of trench warfare, despite the war of movement from August to December 1914 costing the French and the Germans The trench warfare that followed had been less costly in men but attrition warfare was indecisive; limited objective attacks under an umbrella of massed heavy artillery-fire could succeed but only at the cost of unlimited duration. Colonel J. F. C. Fuller, formerly the Chief of Staff of the Tank Corps, proposed an all-tank force, which would operate independently against enemy headquarters and lines of communication. Less radical theorists such as the historian and former British army officer Basil Liddell Hart, advocated mechanised forces of all arms, able to carry out operations of war other than the all-out offensive. Giffard LeQuesne Martel, a third influential reformer, proposed that tanks should be subordinated to infantry formations, while many cavalry officers maintained that the horse still had a part to play on a modern battlefield, in spite of all evidence to the contrary on the Western Front in the First World War.