Tank classification is a taxonomy of identifying either the intended role or weight class of tanks. The classification by role was used primarily during the developmental stage of the national armoured forces, and referred to the doctrinal and force structure utility of the tanks based on design emphasis. The weight classification is used in the same way truck classification is used, and is intended to accommodate logistic requirements of the tanks. Many classification systems have been used over a hundred years of tank history. An early division in the definition of roles was between infantry tanks intended to focus on supporting infantry in the assault, and cruiser tanks intended for classic cavalry missions of exploitation, screening and reconnaissance. As World War II progressed, the separation of "infantry" and "cruiser" roles generally disappeared and the "universal tank" started to take over. Classification has always been determined by the prevailing theories of armoured warfare, which have been altered in turn by rapid advances in technology. No one classification system works across all periods or all nations; in particular, weight-based classification was inconsistent between countries and eras. With the worldwide adoption of the modern main battle tank designs, which favour a modular universal design, these sorts of classifications are mostly eliminated from modern terminology. All main battle tanks are typically armed with weapons with similar characteristics but some may be armoured more than others. These are complemented with light tanks, typically in the role of (armed) reconnaissance. Development of tank classification schemes Development of a tank classification system started in World War I, when tanks were separated into light tanks and tankettes, medium tanks, and heavy tanks, based on size and weight. Heavy tanks were required to be large to cross trenches, and consequently weighed a lot. Medium tanks were smaller and had help to cross trenches so weighed less. Light tanks were much smaller and lightweight, allowing transport on lorries (trucks). These tanks started to be used in different roles based on armour and mobility. Light tanks could provide mobile machine gun support for infantry, medium tanks could be used to react and exploit situational advantages, heavy tanks could be used for the main advance. As tank doctrine developed, the role of tanks started to be defined. Initially based on naval ideas, in late 1916 Captain Giffard Le Quesne Martel (later Major General Sir) proposed a tank army formed of Destroyer tanks,