First Large-Scale Invasion

The First Large-Scale Invasion was an attack by Trion Soldiers in Mikado City four and a half years before the start of the series. It killed over 1,200 people, and over 400 people are still missing.

Summary
The attack was carried out by an unknown Neighbor nation on Mikado City. Conventional weapons proved ineffective against the alien invaders. In just two days over 1,200 people died, and over 400 were missing, some of whom were presumably abducted. The eastern portion of the city was destroyed, causing many to lose their homes. The attack was ended by Border, which went public after the incident.

Trivia

 * The large-scale invasion started on a Sunday.