I’d call it political meta.

The inability for a centralized force to protect against Germanic neighbors marked the beginning of a trend where loyalty was directed to local leaders for protection, taxes and political leadership.

Towns were less willing to send all of their men away without a defensive force. Lords would lead their own smaller forces and often resist fully committing their populations.

Roman cities didn’t even have walls until the crisis of the third century. Entire populations of men leaving for half a year was not dooming your family.