How Effective were Spears Against Cavalry?

[M. Demetrius]

Well, if rows of sharp points directed toward the horses were not somewhat effective, they would not have used the tactic for over 2000 years or so. And should our warfare take a step back to that level, they'll use it again, whether sharpened saplings, stone tips, or elaborately forged metal points, they'll do the same thing. Once the horeseman is unceremonially launched into the ranks of infantry, his longevity index decreases dramatically. The third and fourth row of infantry are glad to help with that, I'd reckon.