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A half-track is a civilian or military vehicle with regular wheels on the front for steering, and caterpillar tracks on the back to propel the vehicle and carry most of the load. The purpose of this combination is to produce a vehicle with the cross-country capabilities of a tank and the handling of a wheeled vehicle.

A Kégresse track from the personal car park of the Tsar

In 1911 the French engineer Adolphe Kégresse converted a number of cars from the personal car park of the Tsar of Russia as half-tracks. His system was named after him: the Kégresse track. From 1916 onward there was a Russian project by the Putilov plant to produce military half-tracks along the same lines using trucks and French track parts.

The primary advantage of a half-track over a full caterpillar-type (or 'crawler') vehicle is the idea of being able to carry its own payload where wheeled vehicles could not go, and where full crawler machines could not traverse with trailers needed to carry a load. Often ballast or "dead weight" was added to full crawlers for improved traction, where a halftrack simply increases its payload.

U.S. WWII half-track in training at Fort Benning

US 9th Armored Division halftracks advance through Engers, Germany 27, 1945

The concept originated with the hauling of logs in the Northeastern US with the Lombard Steam Log Hauler built by Alvin Lombard of Waterville, Maine, from 1899 through 1917. Resembling a railroad steam locomotive with sled steerage (or wheels) in front, and crawlers driven by chains instead of the driver wheels of a locomotive.

By 1907, dog and pony show operator H.H. Linn abandoned his gas and steam powered four and six wheel drive creations and had Lombard build a motor home/traction engine run by a underslung four cylinder gasoline engine to travel the unimproved roads of the day, wheels in front, tracks in rear, the first payload carrying halftrack. By 1909 this was replaced by a smaller machine with two wheels in front and a single track in rear because rural wooden bridges presented problems. Stability issues, coupled with a dispute between Linn and Lombard, resulted in Linn building and putting his own improved civilian halftrack style machines on the market, Lombard attempted to follow but for the most part remained a pulling machine. Linn would later copyright "HAFTRAK" and "CATRUK" as trademarks, the latter for a halftrack meant to convert hydraulically from truck to crawler configuration.

In the early days of bulldozers, Holt tractors had tricycle steering, owing to engineering difficulties with the caterpillars. The Holt tractors went on to become the basis for the Mark I tanks, the Schneider CA1 tank, and the German A7V tank. The Holt would be renamed the Caterpillar 60, launching an industry.

Also of note are the "snowmobile" attachments for automobiles built by White, Snowbird and others, for converting Fords to halftrack configuration.

There were many civilian half-track experiments in the 1920s and 1930s. The Citroën company sponsored several scientific expeditions crossing deserts in North Africa and Central Asia, using their autochenilles. These would be studied by the US Army to design the military M2 Half Track Car.

With the snow and ice of Canada in mind Joseph-Armand Bombardier developed 7 and 12 passenger half-track autoneiges in the 1930s, starting what would become the Bombardier industrial conglomerate. The Bombardier half-tracks had tracks for propulsion in the rear and skis for steering in front. The skis could be replaced by wheels in the summer, but was uncommon.

German SdKfz 11 half-track

Half-tracks were used extensively in World War II by all sides, especially the Germans (SdKfz 11, SdKfz 250, SdKfz 251) and Americans (M2 and M3 Half-track), but soon fell out of favor, replaced with fully-tracked or fully-wheeled vehicles. Half-tracks were used primarily as armored personnel carriers, but also saw duty as mortar carriers, self-propelled anti-aircraft guns, self-propelled anti-tank guns, artillery tractors, armored fighting vehicles and many other tasks.

During the Cold War half-tracks were used by the NATO members and saw combat service in the First Indochina War and the Algeria War. Half-tracks were still in use by the Israeli Army until recently, where they were deemed to outperform fully-tracked and fully-wheeled vehicles for non-combat payload tasks such as carrying telecommunication equipment.

One of their main advantages is that they were drivable by anyone able to drive a car or truck, with additional steering provided by track braking applied from the steering wheel, although not a feature in the American halftrack.