One such operation was the planned Sontaran invasion of Gallifrey. A Special Space Service unit under Commander Stor was to seize the Capitol and widen the gap in the transduction barrier, allowing the rest of his battle fleet to land. Though there were only a handful of Sontarans, they were more than a match for the Chancellery Guard and their allies, as both stasers and K9's blaster were ineffective against the Sontaran armour. The invasion failed when Stor and his remaining troopers were killed by the De-mat Gun wielded by the Fourth Doctor.