From the first days when mankind began to use heavy missile weapons to breach castle walls, the armies needed some form of vehicle to carry the ammunition they used to their weapons. Most often pulled by slaves or domesticated animals, these ammunition carriers worked for thousands of years. During the great wars of the 20th century, combustion engines replaced the slaves, animals, and the steam engines that had been experimented with, greatly increasing the speed of the carrier, especially over a long range. These basic self-propelled ammunition carriers have remained with us ever since, used on every world of the Human Sphere to keep their militaries ready to fight.
         The oldest, and still most common, ammunition carriers have wheeled chassis that allow them to move on normal civilian roads without damaging them. The tracked chassis was introduced during the great wars of the 20th century and is used if they are expected to be forced into extremely rough terrain. VTOL carriers became common during the brush fire wars that followed and proved especially useful during the Islamic Jihad and the Second Soviet Civil War. First introduced during that last war, the hover chassis has impressive ground speed that has kept them in use since.
         Any soldier throughout the Human Sphere can be expected to work with any number of these units in any of their configurations throughout their career.