Force field?

Cool. But, don't stop there. Also have alien attacks from outer space, with AI flying saucers. And, have huge blobs (not referring to FDBs here) that roam around on the ground consuming tanks and other GVs. Have live, AI-controlled giant squids that can pull CVs/ships under, unless killed first. And, create special targets, that when killed give the killer "Populous" type powers (the ability to create swamps with tank-swallowing quicksand, earthquakes, etc.).
Okay, so I've had too much coffee...