Before the machine mutiny, Keppler used to share a common border with Sorus. The districts were separated by a great wall that had checkpoints on both sides. Since Keppler was Solis' administrative district, its borders were heavily fortified. One had to pass through several checkpoints to get clearance for entering the district.
When the machines hit Keppler they first brought down its walls with heavy artillery bombardment, and then the infantry units moved in to neutralize the guards protecting the border. What followed was a brutal and bloody battle at the checkpoints. The guards took down hundreds of XL11s and Revenants but were eventually wiped out when the main fighting force led by an android showed up.
