Emergence Day, or E-Day is the day that the Locust Hoard emerged from the ground and attacked the Human populace. The Locusts attacked every major city across Sera. The COG, or Gears fell back to Jacinto Plateau, where the Locusts couldn't penetrate the walls. The COG Commanders then ordered Orbital Beams to attack Sera. They thought that this would exterminate the Locusts, but the Locusts retreated into their underground tunnels and were protected, but the Orbital Beams destroyed over 90% of Sera, killed many humans, and left others homeless, they were called the Stranded.
The Outcome of Emergence Day was in the Humans favor, but, at the time of E-Day, the Humans had been in a civil war for years and this had greatly weakened there forces, so the Locusts had an advantage in the battle. The Locusts were beat back by the Orbital Beams, but they were not dead. So, even though the Humans were small in numbers they had won E-Day. But the Locusts would later emerge again, and this time they didn't lose.