most important for cavalry was the ability to quickly attack enemy cavalry or scattered infantry with lances and sabres. Speed reduced the time vulnerable to gunfire, but still closed formations became impossible to defeat. This tactic was a striking surprise of Mongolian light cavalry in the battle of the Kalka River. The alternative was to use them as dragoons, reaching their positions quickly, dismounting, and fighting like infantry, often with projectile weapons. Such a way of fighting had started in Europe at least in the mid-13th century with mounted longbow and crossbow archers, but was also employed by the Mongols with their Buryatian longbows. Cavalry in modern warfare Cavalry is featured in modern warfare with cavalrymen retaining the light cavalry missions, albeit with but the missions of reconnaissance and security remain the same. Heavy cavalry, as such, has its role of shock effect fulfilled by tanks and other armoured fighting vehicles. Since the early 20th century, the use of horses and other animals for frontline cavalry has been largely supplanted by infantry fighting vehicles and armored cars. The first regular cavalry unit to mechanize was the 11th Hussars of the British Army, switching from horses to armored cars in 1928. Since then, many cavalry units have mechanized and switched to armored vehicles and armed helicopters, with horses only being used for ceremonial purposes, if not phased out of service entirely. However, some modern units, such as the Indian Army's 61st Cavalry and some People's Liberation Army's border units in Xinjiang and Inner Mongolia, continue to use horses on deployments. Examples of modern military vehicles built specifically for the cavalry role include the M3 Bradley CFV and the M113 ACAV. Air cavalry Air cavalry, originally sky cavalry is a United States Army term that refers to helicopter-equipped units that perform reconnaissance, security, and economy-of-force missions. The term and unit designation properly only refers to those squadrons (i.e., battalion-level organizations), and some independent troops (i.e., companies), affiliated with historical U.S. cavalry regiments, that perform the traditional cavalry mission. After the Vietnam War, there also existed one independent brigade-sized air cavalry organization, the 6th Air Cavalry Combat Brigade. U.S. air cavalry squadrons consisted of three air cavalry troops, one armored cavalry troop, and a headquarters and headquarters troop. The air cavalry troops consisted of an aero-scout platoon, an aero-weapons platoon, an aero-rifle platoon, a service platoon, and a headquarters and operations platoon. The