Military expenditure consumed roughly eighty percent of Song government revenue. Early Southern Song army spending reached about 9.6 million strings of cash annually and increased as armament expanded. With so much spending concentrated in the military, attempts to save money threatened the force needed against powerful neighbours. Giving generals greater autonomy risked restoring the local power that the dynasty wanted to restrain. Rotating battalions and commanders between frontier and central postings on a roughly three-year cycle limited attachment to particular places and commands. The system helped maintain loyalty, but moving forces and rebuilding command relationships cost money.
Chapter · 34:58-39:00
The cost of keeping Song commanders under control
The Song's large military budget and costly rotation system linked defence spending directly to the problem of controlling generals.