Battlefield role
Anti-cavalry infantry that protects economy lines and ranged units from mounted raids.
Spearmen are the classic strategic deterrent: their job is mostly to exist. A visible spear line near your economy makes cavalry raids unprofitable, which means the raid often never comes.
The counter relationship is positional, not magical. Spears beat cavalry that engages them; cavalry that ignores the spears and hits an undefended flank is still winning. Place spearmen where the enemy must fight them, and they’re among the most efficient resources you’ll ever spend.