Operation Ragnarok

Operation Ragnarok (ラグナロク作戦) is the main event of Mega Man Zero 4, which involves Dr. Weil using Ragnarok to destroy Area Zero.

Background
Prior to the events of Mega Man Zero 4, with Copy X dead, Dr. Weil invokes Ordinance #8 and becomes leader of Neo Arcadia by unanimous vote. He then uses Neo Arcadia's resources as he sees fit, to gain control of Reploids through the combined powers of the Dark Elf and Omega, in order to punish the citizens of Neo Arcadia for his banishment. Though Zero destroys Omega in the end of Mega Man Zero 3, Weil remains ruler of Neo Arcadia.

It was for this reason that a caravan moved from Neo Arcadia to this location to escape from Dr. Weil's tyranny. Later, a mobile unit from the Resistance is stationed outside the area for protection. To leave humans without a place to escape, Dr. Weil sends Craft and the Einherjar Eight Warriors to destroy Area Zero, and they are just a diversion while he prepares Operation Ragnarok.

Prelude
The second phase of the operation, is to attempt to use Ragnarok to destroy Area Zero and thus turn every place outside Neo Arcadia into wasteland. This would have left all under his control in Neo Arcadia without a place to escape from him. In order to ensure that Ragnarok was completed, he deliberately left the details of Ragnarok vague to his enemies, and also had each of the Einharjer Eight Warriors lead a different front on Area Zero (A mobile particle cannon targeting Area Zero for Heat Genblem, infecting a nearby ancient machine city with a computer virus as a means to make it a frontline base for Area Zero for Popla Cocapetri, incinerating Area Zero with an overloaded Artificial Sun with Sol Titanion, pouring acid rain to Area Zero via a flying fortress with Pegasolta Eclair, using a massive electromagnetic generator to disrupt the overall area with magnetic waves with Mino Magnus, having a fake jungle overtake the natural environment of Area Zero via plant nanomachines with Noble Mandrago, reactivating an old laboratory containing potentially dangerous and uncontrollable experiments with Fenri Lunaedge, and having a drill-equipped submarine drill down to a fault line in the ocean and then detonate with Tech Kraken), as a means of both destroying Area Zero without the need of Ragnarok, and to distract the Resistance and the Caravan until Ragnarok is completed.

Climax
As the Resistance trailer, mostly with the help of Zero, finished demolishing all the Weil's forces outside as well as inner of Area Zero, Craft gone missing for unknown reason. Weil, apparently with the completed Ragnarok at the time, transferred a warning to the Resistance, leaving them a warning. Before Zero could take any action, the connection was interrupted by a transmission from Ragnarok itself. It was shockingly revealed: Craft has removed the remote control system, and took the manual control of Ragnarok, and it is now currently aimed at Neo Arcadia. Zero was transferred somewhat further to the control base, however, right before he reach Craft's control room, the fully charged cannon has fired as an attempt of Craft to kill Weil as well as destroying Neo Arcadia, believing it's the only way for human and the caravan particularly to survive.

Even though Zero destroyed Craft right after, things which happened can't be changed. which was unseen to Craft: Neo Arcadia was completely devastated, caused over 20,000,000 casualties, leaving Earth's main government at the time in a post-apocalyptic state. To make things worse, after Craft's death, it's shown that Weil survived. He alerts Ragnarok's activity by firing a shot again, and attempts to use Ragnarok again, this time by crashing the satellite into Area Zero to destroy it. However, this attempt was sabotaged by Zero when he confronted Dr. Weil. The madman fused with the station's core to battle Zero, but Zero manages to defeat him, destroying the station in the process. Zero perishes/disappears in the explosion, thus ending the series.

Epilogue
The operation has ended pathetically to Weil, turns everything against himself and his taken government. Despite many loss, Neo Arcadia and its havocs became history, a trace in humankind's past, with the death of a great part of living beings, as well Dr. Weil's death and the heroic sacrifice of Zero, peace finally has comeback to Earth, leading to the new generation to arise and reconstruct the now greyed areas. The new government has been established at Area Zero for centuries later, to become the Cinq Ville, the largest city in the world in the end. Their souls and the Four guardians are still living in the incarnation of Biometals created by Ciel, still continue to protect the humans, the Reploids as well as against Model W.