You need Units to protect your Base, Black Sites, and Alliance HQ, raid other players' Bases and Alliance HQs, complete Special Ops, and to capture and extract Resources from Resource Caches.
To hire Units, you must have researched the Tech corresponding to the Unit you want to hire, and have constructed the required Buildings. For example, to hire Sekira Drones, you must have researched the “Sekira Drones” Tech and built the Armor Depot.
You may pay for Unit Hiring using the game’s primary Resources, or by using Diamonds. You can hire Units by tapping on the “Units” tab at the bottom of your screen.
All Units consume Rations.