In Wars of Reaving Supplemental, on p. 2, it is stated that "No formalized formations larger than a Sept were ever noted." However, especially given that it's an in-universe report, it recently occurred to me that this doesn't mean there weren't any, simply none noted by any of the Clan Watches. Large, cohesive Society forces consisting of multiple Septs were seen in a few instances on worlds like Ironhold and Babylon; were these purely ad-hoc formations with each Sept or group of Treys acting more or less under their own initiative (in a tactical sense—obviously they had to at least be communicating at the theater level insofar as organizing arrival times and transport), or was there any sort of formal order of battle, even if only as a temporary task force?
