The System is the main antagonistic force from the Zanac series.
The System is a huge computer network created ages ago by a ancient extraterrestrial culture, containing all of their knowledge. Linked to the System were various Icons scattered around the galaxy, which served both as keys to activate the System and as a test for future civilizations which found it. If these people opened the Icon correctly in a non-violent way, the System would bestow them with all of their knowledge. However, if these people opened it with brute force, the System would annihilate them.
As humanity developed the technology for faster-than-light travel, many expeditions were sent to investigate the stars. One of these expedition found one of the Icons and, suspecting it was hiding something valuable, turned their spacecraft guns on it. This triggered the activation of the System, which immediately began its assault on humanity.
While the System prepared its attack, another expedition found another Icon and was able to open it correctly. This Icon sent a signal for the System ordering it to stop the attack. However, due to how much tyme the System had spent waiting it degraded to the point that it was now nothing but a instrument of mass destruction, so it disregarder the Icon's order and began attacking Earth.
Without much options, humaity prepared themselves for the impending attack, despite the overwhelming difference in strength. However, another Icon is found, which gives people information in how to properly fight the System. Being a tactical computer, the System was designed to fight against entire armies, making an all-out against it practically suicide, but if instead a small-scale attack with a single ship was used, the System would have difficulty fighting it and would thus become vulnerable. With this valuable information, Earth's military constructs the AFX-6502 Zanac space fighter, which is then sent to fight the System's forces to save humanity.
The Zanac fights a fierce battle, but despite the odds it successfully destroys the System core. However, the fight was far from over. As it turned out, the System had multiplied itself through its long existence, meaning that multiple Systems existed, so even though one System was destroyed another would soon activate and continue the fight.
Humanity spends long 30 years fighting the Systems, with no signals of end to this struggle. However, during one of the System's destruction a pilot discovers a unit escaping from it. By analyzing the signals emitted from this unit, it is discovered that the System works on a hierarchy, with a higher System unit existing. Since the System was originally a singular computer, this Original System was the highest on the hierarchy, meaning that if it got destroyed the chain of command would be broken and all Systems would be immediately deactivated.
Through intense research, humanity finds out this Original System was much more powerful than all other Systems. If they attacked it, humanity would become a target, and if the attack failed that would mean the end of all human life. Faced with no other option, Earth's military picks their three finest pilots and their strongest ships, forming the Zanac Unit to launch the last offensive against the System.
As predicted, the Original System prepares it's defenses against the attack and launches a strong offensive against the Zanac Unit, which manages to reach the core of the Original System and destroy it after a tough battle. With the Original System destroyed, all other System units immediately deactivate, finally putting an end to this long war.