The Armored Personnel Unit (APU) was a hydraulic mechanized walker designed for combat. They formed part of the primary line of defense for Zion.
More than 120,000 units were produced by the time of the Battle of Zion, only 350 remain (although in screen when Captain Mifune gives his speech there are only around 70 APUs present). Its main armament are two 30mm rapid-fire cannons attached to its arms. All motion of the APU is controlled by the operator's hands, including its legs. APU operators were required to pass a training program.
APU ammunition is reloaded by hand with the help of a special crane located on the back of each unit. To reload the cannons, a runner with a cart loaded with ammo will have to run out in the middle of the battle to jam the boxes of ammo into the APU. This is extremely dangerous for both the pilot and the runner, as the pilot cannot defend himself or the runner during the reload. After the reload process is finished, the ammunition will be loaded to the gun via a flexible belt feed. When the ammo has run out the pilot is trained to pack their gun into their holster, allowing the belt feed to reattach automatically once the ammunition becomes available.
APU armor is ironically minimal, favoring speed and firepower over bulky protection. The reason being that in all likelihood armor would only mean a slower death for the pilot if machines disabled his APU. The armor originally used on APUs, as seen on the UN version, would do very little to defend against machines who've proven many times to be capable of cutting open or slicing quite quickly through the toughest armors Zion can produce. To some people, this separation of man and machine with a lacking cockpit is also symbolic of who is in control and who is not.
The APUs are armed with two 30mm machine-guns. It lacks any actual body armor and is often helpless if attacked by a swarm of Sentinels. However, they work well if in a group against a swarm.
APUs of the Second RenaissanceEdit
The earliest forms of APUs go back as far the beginning of the Machine War. These forerunners used by the UN forces of the time were multifaceted; featuring enclosed cockpits, reinforced armor, some flight capability and a targeting system interface. A drawback to this design was it didn't seem to have as much arm movement as a Zion APU and appeared very restrictive in its shooting. The first APUs fought against 01's Machine Army and were originally designed for combat with heavily tainted areas in mind, hence the enclosed design.
Though comparatively advanced to the contemporary Zion model, they still had little effect against 01's combat harvesters. During many instances, harvesters were seen binding the APUs' arms with their tentacles, open the enclosed cockpit with a laser and kill or even harvest the pilot. They were also seen to need a large amount of maintenance.
After humans were enslaved in the Matrix and both Zion and the resistance was formed, production began on new APUs from the limited resources available. After a while, they were able to produce as many APUs as half of Zion's population. The entire APU corps was deployed in defense of the Dock. All of the APUs except 13 units seem to have been destroyed during the brutal battle, and the remaining 13 were destroyed after the Mjolnir hovercraft activated its EMP inside the Dock, wiping out the first wave of Sentinels. Though they are a formidable defense, during the Battle of Zion, they are eventually overwhelmed by the large swarm of Sentinels that flood the Dock.
- In the defense of the dock the pilots seem to operate in squads of three to four APUs back to back, allowing all arcs of fire to be covered. According to the artists working on the APUs, a cockpit would make practical sense but they decide that it would be a lot easier to identify characters such as Captain Mifune without one. The three man formation also enables faster response on 360 degree sign and survivability as the ammo recharging process can be guarded by the remaining APUs in the squad.
- The APU bears a resemblance to the power-loader utility exoskeleton from Aliens (1986) and, later, the Cyclops Power Armour seen in Halo Wars as well as the AMP Suit from Avatar (2009).
- A Half-Life mod called Zion Warcry has been developed, allowing you to play as an APU in the Battle of Zion. Zion Warcry on Moddb.