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. To protect the exposed gunner and reloader, a small escort of infantry is send along with the reloader to provide protection, however, the job remains highly dangerous for all the people involved. 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, aside from Zion's limited industrial capacity. 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 used by humans during the first war were more "advanced" than those used in Zion, the cockpit was located in the center of the exoskeleton, in the "chest" of the APU and unlike the Zion model, this version was piloted when the operator placed his legs and arms in the exoskeleton joints, and not by means of controls, ensuring their grip, in addition to being secured by bolts grip that maintained it, making the pilot not lose control of the APU in case of strong impacts in the middle of the fighting, the hatch was equipped with a visor that provided the only possibility to the outside, although this was due to the sealed design of the Suit itself, it seems that the visor is adjusted to a predetermined height and it is not possible that they are not modifiable, which could indicate that the APU could only be operated by individuals or pilots of a certain height.
Likewise, the suit was heavily armored, in addition to having incredible mobility in straight-line races, reaching extreme speeds, likewise, the APU weapons were directly connected to the exoskeleton arm, but unlike the Zion model, mobility was very limited. , more because the weapon was mottled together possibly with the ammunition, the weapon was mounted on one side of the arm, which ended in a kind of flat fist, but not as a weapon, like this in the later model of Zion, which made that the angle of fire was seriously limited, being more commonly accepted that the mobility problem was due to its objective of frontal lightning attacks and attacks of falling from the sky, not for combat against enemies by air (something that would play against them in subsequent years).
Even with all this, the result was that the pilot could not take off the exoskeleton if the central hatch that covered the chest was torn off, in addition, the extremities, both arms and legs were effectively tied to the extremities, making the operator unable to escape, causing him to be trapped. This was a failure that the UN model had throughout the conflict, a weak point that would be constantly exploited by the Machines, the Harvesters could tear off the armored hatch, and then separate the pilot from the exoskeleton, being dismembered by having his limbs connected to the suit.
Despite all this APU model it was quite effective during the first of the human counteroffensive after the launch of Dark Storm, being used in frontal assaults against the legions of 01 and lightning attacks, making short flights, thanks to its thrusters placed in the part rear of the exoskeleton, although the latter seems to be very difficult to fly, in addition to having a fairly short flight time, only used for jumps or flights over relatively short distances. These propellants would later be used to a great extent in the withdrawals that human forces suffered during the war, when the APUs were about to be surrounded or cornered, they escaped using them, although this could end the fuel that in the long run. It would end up leaving the exoskeleton sold before the Machines, because the collectors and sentries could surround these models and then destroy them. Even with this, the APU would be used in large quantities by human forces, although to a large extent they had become enormously ineffective against the Machines, even more so when the enormous amount of these could immobilize them, more still the shortcomings that these models had shown were still launched against the legions of Machines, which they simply destroyed by launching the sentries from the rear or from above.
APU of the United Nation
The armament of the APUs from the very early years of the centuries-spanning Machine War is unknown, although the normal armaments used in Zion were a pair of large-caliber automatic cannons in both arms, which can vary in caliber from 20mm to 30mm (as used in Zion) these were clarified and placed on the arm, with the barrel next to its firing system and the ammunition stored in the arm compartment, this possibly avoided jamming in the middle of combat from continuous shots, something very important for humans during the huge counteroffensive on the troops of 01, since they were equipped to face the waves of Machines, firing continuously to decimate them and then go through these formations, something that was important in the attacks, since the jamming of the cannons in the middle Combat could cause the loss of half of the APU's fire and offensive power, although this system would also have its flaws.
Unfortunately, the weapons of these APUs proved to be very inefficient against the more advanced models of Sentinels, Collectors and Pyramid Towers of 01 when the war turned in favor of the Machines, these models caused havoc before them, in addition, an enormous limitation that This APU model returned more inefficient was the little flexibility of the arms, which resulted in the pilot having very few chances against the fast sentries of 01, since being designed for the frontal attack and not defending against enemies that came by air (if it did not activate its thrusters), they could easily be attacked from behind by a sentry which would have the facility to shoot down the exoskeleton knowing that the arm of the same would not have a sufficient angle of fire to damage it, so these models Forerunners would have to go in pairs or triangles of fire to avoid attack from the rear.
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. Footage from the Second Renaissance suggest that the earlier versions had different but interchangeable weapon subsystems.
APUs of the Second Renaissance
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 as the enclosed cockpit and targeting system limit its line of sight. 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. During this time, the APUs used by the UN were involved in crude and destructive combat against the Machine armies of 01, during which time this APU model eventually became a mass production variant (such as that used in Zion centuries later), being distributed by the UN forces all over the planet.
However, the US forces and allies of the West were the ones who used this type of exoskeletons more than their other allies, seeing in use from the massive offensive to the conclusion of the destruction of the Sky during Operation Dark Storm, having a high success against the formations of the humanoid Machines of 01 during the first years of the world counteroffensive, however as the war progressed and 01 was improving his soldiers, abandoning the previous models and making the collective of Machines more dehumanized in favor of a hive mind, the human forces were finally stopped and then put in successive unstoppable retreats.
It was on the European continent where these APU units would be used, being used in the Ardennes where, using their flight capabilities, they made lightning attacks against the forces of 01, but only delaying the advance until the human forces withdrew from the continent thus leaving Europe to fall at the hands of the Machines. The human forces would use these exoskeletons in the confrontations that took place in the United Kingdom, before the territory was completely conquered by the Machines, the British and American forces together with the continental European remnants made a use Extensive of the APUs in the campaign, although eventually they would be defeated, the human forces would finally withdraw to Greenland where an enormous number (hundreds of thousands is theorized) of these units were used in the defense of the human fortress on the island.
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.
They were also used in the defense of the United States and Canada respectively, during the invasion of the west coast, more especially Utah, the American forces used these units extensively, having a poor success in the best of cases, despite the iron and steel industry. Desperately tough human resistance, during the decisive battle in Central America between the combined armies of the United States and the American countries where thousands of APUs were destroyed by the Machines, being seen in action for the last time during the fall of the human fortress in Greenland, where the armies that had managed to repel the forces of 01 would be destroyed (having lost their supply line when Canada was taken) thousands of these were used by the defenders, although with little success during this same battle.
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. While lacking of jump booster seen in the earlier version, ironically this version's lack of targeting system actually allowed its pilot to train both of the gun much better. The targeting system is manual, relying on a simple reticle on the handle. 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 proved a formidable defense during the Battle of Zion, they were eventually overwhelmed by the large swarm of Sentinels that flooded 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 Armor seen in Halo Wars as well as the AMP Suit from Avatar (2009).
- A Half-Life mod called Zion Warcry was developed in 2007. The mod allows you to play as an APU in the Battle of Zion. As of 2019, it is 99% complete as a private project, but waiting for acknowledgement and approval from Warner Bros, before being publicly released.