Decimal organization built on extreme loyalty

Genghis Khan organized his army on a decimal system (squads of 10, up to 1,000) staffed by loyal commoners rather than untrustworthy kin, with mutual life-risking obligations within each squad of ten, no-man-left-behind ethics, left/right wings (east/west), a central bodyguard, and vanguard/rearguard, creating extreme coordination and discipline.