The Third Battle of Rhen Var occurred when the Mandalorian Supercommandos were nearly entirely destroyed by this time, but a group still supporting Alpha-02's ideas set up a Separatist base on Rhen Var. SARC Squad and the 501st were sent to destroy it.
They had a harsh time, but when SARC Squad deactivated OOM-9b, they broke his connection with the security droids, and all the security droids in the control sphere were shut down. The 501st just got in and found about 20 misfit clones and hundreds of dead droids. They received nearly all of the credit for that victory. Only SARC squad's advisors knew of SARC's contributions.