… Officers only get 2-3 year commands. Normal rotation… if you don't have this type of rotation then your military starts to age as promotions stagnate. You want a young military and fresh commanders to bring change and new ideas to the command.
… I said Commanders. Most of the X'd Officers are Combatant Commanders (CCDR): EUCOM, CENTCOM, NORTHCOM, SOCOM, SOUTHCOM, AFRICOM, TRANSCOM, STRATCOM, CYBERCOM (NSA), and PACOM. The Joint Chiefs of Staff are just that - staff, NOT Commanders. CCDRs answer to the SECDEF and POTUS.