- This article is about an in-universe event. For the in-game mission, see Megalith (mission).
Operation Judgement Day was the final operation carried out by the Independent State Allied Forces during the Continental War. The operation objective was to disable and destroy the Erusians' Megalith missile-launch facility, which had been completed sometime around the war's official conclusion on September 19, 2005.
The ISAF had been aware of Megalith's development since around the time of Stonehenge's destruction. During the final months of the war, Erusea had accelerated Megalith's construction in an effort to complete the superweapon before the Allies could achieve total victory. Conversely, the ISAF had pushed to end the war before Megalith could be activated and unleash considerable damage across Usea.
Following Erusea's official capitulation on September 19, a group of young Erusian officers eluded ISAF capture and seized control of Megalith. Refusing to accept their nation's defeat, this group activated the missile-launch facility and planned to use it as a retaliatory weapon of mass destruction. As a missile-launch facility, Megalith was capable of targeting Ulysses fragments and altering their orbits to descend and impact the planet's surface. The only way to destroy the heavily fortified facility would be to hit it from the inside.
On the morning of September 26, one week after the armistice was signed, the ISAF's newly bolstered Mobius Squadron, flying under the command of Mobius 1, was dispatched to the Twinkle Islands off the western coast of Usea. As the ISAF fighters approached the facility, they were confronted by the Megalith defense squadron—a large force of rookie Erusian pilots flying Su-37 Terminators in Yellow Squadron's livery. Despite the defense squadron's advanced aircraft, the veteran pilots of Mobius Squadron shot down all of the Erusian fighters following an intense dogfight over the ocean.
Meanwhile, an ISAF special forces unit infiltrated the Megalith facility and attempted to seize control of the weapon's internal control systems. However, a series of security doors blocked the infiltration team's path, trapping them on the thirteenth floor. In a spectacular display of piloting, Mobius 1 flew into the missile port grooves and disabled Megalith's three primary power generators. The resulting blackout disengaged the electronic locks, and the special forces team secured control of the sub-control room. From there, the infiltration team opened the panels that sealed the central silo's heat vent. Mobius 1 flew into this narrow opening, destroyed the large missile stored within, and escaped out the top of the silo. The ensuing explosion set off a chain reaction within Megalith, which destroyed the facility.
The loss of Megalith signaled the end of Erusea's military dominance over the nations of Usea. With the last of the Erusian resistance suppressed, the ISAF would proceed to occupy Erusea and oversee the establishment of a new Erusian government. As part of the ISAF's terms of surrender, the Erusian military would be significantly downsized, and reconstruction efforts finally began across the Usean continent.