It wasn't a terrorist group, it had control of the entire country.
This.
The NMSSDA Colonel takes out a PDA, looks at it, then begins walking down another alleyway. He comes out on a street, abandoned and ruined. He runs down the street, the entire team following. They soon arrive at the next substation, and they repeat the same process as before, shutting down the rest of the power in the city.
The Colonel picks up his radio, "Power is out, railgun defenses should be down. You are go for invasion."
Meanwhile, at the forward operations base, the radio operator announces the message, and soldiers, MBT's, MRGS's, and NGET's advanced, they begin marching forward, taking down the opposing force bit by bit.