According to the joint indictment, Mrksic was the commander of the JNA's 1st Guards Motorised Brigade, which bore prime responsibility for the three-month siege of Vukovar that led to its eventual fall in November 1991.
Prema zajedničkoj optužnici Mrkšić je bio zapovjednik 1. Gardijske motorizirane brigade JNA koja je snosila glavnu odgovornost za tromjesečnu opsadu Vukovara koja je dovela do konačnog pada grada u studenom 1991. godine.