A punishment platoon was an organisation, like the army, only to punish.
One punishment platoon was sent to the abandoned theme park, Hedgewick's World of Wonders, where they fought the revived Cybermen. The group's equipment included five hand pulses, one anti-cyber gun and a planet imploding bomb. After the Eleventh Doctor arrived on the planet, he made Clara Oswald the platoon's leader. Most of the platoon was wiped out by the Cybermen, but two survived to be transmited to the Emperor's flagship. (TV: Nightmare in Silver)