NATO officially decommissioned Tesla Coils in particular due to the habit of the weapon in particular to start forest fires and electrify people touching the base of the dangerous electrically-charged device, causing a few unintentional deaths of curious civilians. Due to the high cost of maintenance, the plans were only moderately well-guarded - no organization that had the capability to steal it was considered as willing to use such an obsolete tool.
How the Forgotten got through the defenses laid around the Tesla Coil is still a mystery, but the Sicarii did somehow manage to steal the Tesla technology directly from a NATO bunker, managing to secure Tesla coils for the forgotten. This daring raid is still considered the Sicarii's biggest moment of triumph to date.
Though the Tesla Coil is beginning to show its age, the electrical charge still poses a threat even to tanks, cooking anything unfortunate enough to ignore the warning of the loud screech of its charging sequence with a barrage of billions of volts of electricity. The Tesla Coil causes infantry to light on fire and leaves little more of vehicles than husks. Unfortunately, due to being older tech, it has some glaring flaws: it can be overwhelmed by sheer numbers, and due to the Tesla Coil's inability to strike high-altitude targets, even a single Orca aircraft can freely assault the structure and destroy its fragile coils. Furthermore, artillery systems are a threat to the stationary defense, utilizing superior range to destroy it from a distance.
-side note, sorry it's been so long since any activity here, we have been waiting for an update to the main game to include a couple of features we need.