Armoured personnel carrier An armoured personnel carrier ( APC ) is type of armoured fighting vehicle designed to transport infantry to the battlefield . APCs are colloquially referred to as ' battle taxis ' or ' battle buses , ' among other things . APCs differs from other AFVs , namely infantry fighting vehicles , due to the weaponry they carry . The Treaty on Conventional Armed Forces in Europe defines Armoured personnel carriers as " " an armoured combat vehicle which is designed and equipped to transport a combat infantry squad and which , as a rule , is armed with an integral or organic weapon of less than 20 millimeters calibre . " " By convention they are not intended to take part in a direct - fire battle , but to provide additional protection from shrapnel and small arms fire . Examples include the American M113 , the French VAB , the Dutch / German GTK Boxer and the Soviet BTR . History . The genesis of the armoured personnel carrier concept was on the Western Front of World War I . In the in the later stage of the war , Allied tanks could break through enemy lines , however the infantry following who were needed to consolidate the gains still faced small arms and artillery fire . Without infantry support , the tanks were isolated and subsequently destroyed . In response , the British introduced the Mark V * , which was a version lengthened to include a troop compartment , and the purpose built Mark IX tank . Though a revolution in armoured doctrine , they had little impact on the war . During World War II , half - track s , notably the M3 and the SdKfz 251 played a role similar to post - war APCs . Over the course of the war APCs evolved from simple armoured cars , with transport capacity , to purpose built vehicles . Obsolete armoured vehicles have often been repurposed as APCs . The inception of this concept was in 1944 , with the introduction Kangaroo type carrier . The initial conversion of 72 M7 Priest self - propelled howitzer s was followed by the conversion of Churchill , M3 Stuart , and most heavily Ram , tank s . A later example of this concept is the Israeli Achzarit . After the war , different specialised APCs were developed . The United States developed a series of tracked vehicles , culminating in the M113 , of which 80 , 000 were made . The BTR - 40 , BTR - 152 , BTR - 60 , BTR - 70 , BTR - 80 and BTR - 90 which each produced in large numbers by the Soviet Union Design . Most armoured personnel carriers use a diesel engine comparable to that used in a large truck or in a typical city bus . The M113 for instance used the same engine as the standard GM city bus . APCs can vary in weight of 6 tons to 40 tons or more ; though a typical vehicle will be between 9 and 20 tons . They typically have a capacity of between 8 and 12 dismountable troops , though some models can carry more than a score . By definition , an APC will have capacity for at least 8 . An APC will have at least one crewman , the driver , with as many as three , a gunner and commander . Mobility . An APC is either wheeled or tracked , or occasionally a combination of the two , as in a half track . Both systems have their own advantages and limitations . Tracked vehicles have more traction offroad and more maneuverability , including a minute turn radius . Wheeled APCs are faster on road , and can cross long distances ; typically , due to the limited lifetime of the tread s , tracked vehicles are transported cross country by rail , or a flatbed truck which may or may not be a purpose built transporter . Many APCs are amphibious . Tracked APCs are powered by their tracks , and wheeled APCs will include propellers or water jet s . Preparations for amphibious operations usually comprises checking the integrity of the hull and folding down a trim vane in front . Water traverse speed varies greatly between vehicles . The max swim speed of the M113 is 3 . 8 mph , whereas the LAV - 25 and AAVP - 7 can reach nearly double that at a maximum of 6 . 5 and 8 . 2 mph , respectively . Armour . APCs must provide a minimum amount of protection against small arms fire to be considered as such , though some provide as much protection as a main battle tank , as is the case of the IDF Namer , which is based on a Merkava tank . Armour is usually composed of steel or aluminium . Some APCs also come with NBC protection , which is intended to provide protection from weapons of mass destruction . Generally APCs will be lighter and less armoured than tanks or IFVs , often being open topped and featuring doors and windows , as seen in the French VAB . Weaponry . An APC carries a primary weapon of at most a 20mm autocannon before falling into the infantry fighting vehicle sub - classification , and will most likely be outfitted with one or more machine guns ranging from 5 . 56mm to 7 . 62mm . The primary weapon will usually be mounted on the top of the vehicle , either a simple pintle mount , in a small turret , or on a remote weapon system . Pintle mounted weapons are rare , due to the lack of crew protection . The World War II Axis half track Sd . Kfz . 251 was equipped with at least one MG42 or MG34 , which could only be aimed in a small arc from whichever end of the vehicle the weapon was mounted and offered minimal protection to the gunner . Turrets , by definition , provides a traversal range of 360 degrees and operator protection . Most APC turrets include a coaxial machine gun ( MG ) alongside the primary weapon ; BTR , BMP , and LAV series carry MGs alongside primary weapons , however the basic MTLB ' s turret carries only a 7 . 62mm MG . A recent advent , remote weapons system s are used in leeu of pintle mounts and provide the same level of operator protection as a turret , with the added benefit of increased visibility without increasing the overall profile of the vehicle . However , unlike in a turret , the weapon cannot be reloaded from inside the vehicle . A common primary gun on an APC is an M2 Browning 50 caliber machine gun , or the equivalent 14 . 5mm KPV heavy machine gun . The Stryker carries an M2 on a CROWS , and many IMVs mount one on a RWS or pintle mount . The 7 . 62mm machine guns like C6 , M240 , FN Minimi and PKT machine guns or the 5 . 56mm M249 are commonly used as coaxial or secondary weapons . Several Eastern personnel carriers have forward facing machine guns in the crew compartment . The AAVP7 mounts an M2 50 caliber as a coaxial machine gun beside a Mark 19 automatic grenade launcher . Occasionally APCs will be equipped with anti - tank guided missiles . According to internation law , armoured personnel carriers allocated to medical purposes will be clearly marked and unarmed . Variants . Infantry Fighting vehicle . The infantry fighting vehicle is a derivative of the APC . Various classes of infantry fighting vehicles are deployed alongside tanks and APCs , in armoured and mechanized forces respectively . The fundamental difference between with an IFV is weaponry beyond the definition outlined in the CFE treaty . Often this increase will be simply the addition of , or increase to , a 25mm or 30mm autocannon . The LAV - III , the primary mechanized infantry vehicle of the Canadian armed forces , is classified as an IFV due solely to its M242 Bushmaster autocannon . The M2 Bradley carries the same weapon and classification , but is heavily armoured , outfitted with TOWs and advanced optics , and serves primarily in US Army alongside M1 Abrams Main battle tanks . The BTR - 90 , which mounts a 30mm autocannon and anti - tank missile , is colloquially referred to as an APC . BTR , literally translated , means " armoured transporter . " However the BMP - 3 , literally " Infantry Combat Vehicle " , is equipped with a 100mm gun and not generalized in the same manner . Infantry Mobility Vehicle . Infantry Mobility vehicle is a neologism to describe a decades old concept of an armoured car with increased mine resistance and passenger protection for use primarily in unconventional theatres of war . Though beginning as early as the 1970s with vehicles such as the South African Casspir , they only came into favour in the 21st century in the post - Soviet geopolitical climate . The American uparmoured Humvee , classified as M1114 , is the epitome of the IMV concept . The M1114 is identical to the Humvee , in both design and function , apart from the addition of several tons of armour . The M1114 was later replaced in the role by the purpose built vehicles of the MRAP program , a series of vehicles inspired by the Casspir . IMVs generally feature a v - hull shaped underbelly with additional crew protection features such as four - point seat belts and seats suspended from the roof or sides of the vehicle . Many feature a remote weapon system in place of a crew - served weapon system . The usually 4x4 IMVs are distinctive from both 8x8 APCs , and 4x4 APCs such as the VAB . They are closer in appearance to civilian armoured cars . The term refers to a wide range of vehicles , though the exact classification is contentious .