86th Engineer (Heavy Ponton) Battalion
Your grandfather was a member of the above. The battalion's primary duties consisted of erecting ponton (pontoon) bridging which enabled tanks and other heavy equipment to perform deep water fording. The battalion is credited with the campaigns you mention but there's no way to accurately determine your grandfather's participation without accessing his and/or the unit's records. 3d Tank Battalion is simply the unit he was assigned to at the time of his release which is why it's listed on his discharge certificate.