An Imperial Méxica Navy Battle Group consists of battle ready deployable ships prepared for tasks reaching up to full-combat situations.
As such, a Battle Group consists of a fleet of ships fully prepared for independent action, centered around a number of battleships. A Battle Group usually consists of dreadnaughts, carriers, heavy cruisers and many smaller ships including repair tenders and resupply vessels. It may also include one or more marine or army - usually Arrow Knight - regiments.
Fleet doctrine dictates that when entering a system from hyperspace a Battle Group transits in a series of evenly spaced concentric spheres, with destroyers and cruisers in the outer perimeter to guard the high value battleships and the vulnerable tenders and troopships. As soon as the outer ring of ships has entered normal space, they deploy countermeasures to further screen the inner ships.