Based on the non-fiction book Brothers in Arms by Lindsay Simpson and Sandra Harvey, Bikie Wars is a dramatised account of the events leading up the 1984 Milperra massacre, a shoot-out between members of the outlaw motorcycle gang the Comancheros and the Bandidos, a group formed from a splinter group of former Comancheros: the massacre left 7 people dead and 28 wounded, and led to 63 murder convictions, 147 manslaughter convictions, and significant changes to NSW gun laws.