Some units within certain factions have special abilities to counteract this balance, ie English archers can use Palings (wooden stakes) to defend their position from a cavalry charge. Spears beat cavalry, cavalry beat archers and archers beat infantry is the combat in its simplest form. It retains the same foundations of base building and rock, paper, scissors combat.
The simple answer is that AoE IV retains the old Age of Empires formula.
