The Military Base — shown on the map as Citadel — is the most dangerous location on the island, and the loot matches the risk.

It's patrolled by armed guards. You can tell their rank by armour colour: green — the easiest, blue — tougher, red — the hardest. Don't come with a bow or spear: bring good weapons, plenty of meds and ideally a team.

An anti-air turret on the base shoots at helicopters.

Killing a guard has a chance to drop a Military Base Keycard. It can't be crafted.

Take the keycard to the radar in the centre, climb to the roof from the outside and insert it into the Access Terminal. The keycard is consumed.

The dish activates and calls airdrops onto the base — everyone nearby is notified, so expect company.

After that the radar goes on cooldown — if you try to activate it during that time, you'll see a "system recharging" message.