Even if they were locked out by the metal casing, the Anrufe could still destroy the city defenses. How? Shut it down. An Electromagnetic Pulse was fired out of the ship towards the city. Several more followed, the EMPs being distributed around the small planet. This should shut down all technology past the metal barrier, but still, if the Anrufe hoped to do more damage, they'd have to get past the metal itself. ACID type nanites were deployed to the small planet below to begin eating through the metal barrier.
