Horse artillery was a type of light, fast-moving, and fast-firing artillery which provided highly mobile fire support, especially to cavalry units. Horse artillery units existed in armies in Europe, the Americas, and Asia, from the early 17th to the mid-20th century. A precursor of modern self-propelled artillery, it consisted of light cannons or howitzers attached to light but sturdy two-wheeled carriages called caissons or limbers, with the individual crewmen riding on horses. This was in contrast to the rest of the field artillery, which were also horse-drawn but whose gunners were normally transported seated on the gun carriage, wagons or limbers.