>>64148152
No unit operates truly independently, chain of command stretches from the President to a private digging a trench in bumfuck nowhere. X-centric just means what level do forces consolidate support assets and that level is usually used as the main "piece" on the board by high command
Brigade centric => when you want to, say, start an offensive you task X specific Brigades for the task,
. Each brigade has its own fires, recon, combat engineers, logistics and other such support units, with upper echelon headquarters providing largely administrative support. This makes each brigade more flexible and better for COIN
Division centric => you use Y divisions for the same task instead. The brigades making up the divisions usually don't have the support units organic to them, these are instead consolidated at the division HQ and are attached to specific brigades for specific missions. This allows you to concentrate force multipliers where they're needed the most. For example a brigade tasked with making a breach in a fortified frontline could be reinforced with three brigades' worth of combat engineers by division HQ. This is a strictly better model for large scale war