Lex Luthor was the longtime nemesis of Superman. During his self-imposed exile, Luthor formed a secret society of super-villain masterminds called the Mankind Liberation Front, using the constant metahuman conflict for serving his own purposes.
Luthor brainwashed Captain Marvel and sent him to blow open the Gulag where Superman and his Justice League had imprisoned troublesome metahumans for reeducation. Batman found this out and, with his Silent Cavalry team, captured the MLF members and incarcerated them.
