MICV-65, short for Mechanized Infantry Combat Vehicle, 1965, was a US Army project that studied a number of armored fighting vehicles that would replace the M113 and M114 as well as take on a variety of new roles. A number of designs were studied as part of the MICV project, but none of the entered service for a variety of reasons. Nevertheless, experience gained in the MICV project eventually led to the M2 Bradley, which incorporates many of the MICV concepts.
World War II opened with the concepts of armored warfare relatively undeveloped. Infantry and armor were generally organized as separate units, which led to problems when the armor would outrace the infantry and then have to stop at various obstacles like rivers or strongpoints. As the war progressed the doctrine of combined arms became better refined, and the need for specialist vehicles to keep the infantry in close contact with the armor became increasingly important. Most of these vehicles were half-tracks, arguably the best known being the German SdKfz 251 and US M3. Other forces adopted expedient measures; the Red Army was famed for having their infantry ride on the top of tanks, an extremely dangerous position, while the Canadians introduced a series of converted tanks known as Kangaroos. The Kangaroo pointed the way forward, offering much better armor than half-tracks and able to keep up with the tanks over rough ground.
In the post-war era most armies, save Germany's, started introducing fully tracked vehicles in the dedicated armored personnel carrier role, including the Soviet BTR-50, British FV432, and perhaps most notable, the US M113. These vehicles generally suffered in terms of range and speed on hard surfaces, and many forces also adopted wheeled vehicles in addition to, or completely replacing the tracked versions. Examples include the British Saracen and most of the Soviet BTR series, which were far more numerous than the tracked BTR-50. In general, wheeled or tracked, these vehicles offered limited protection and were not expected to join in the actual fighting; they would keep the infantry in close proximity with the armor during maneuvers, and then offload their infantry before retreating to safer areas. In US service they were derided as "battlefield taxis".