The Makedonian phalanx -- why such depth?

[PMBardunias]

By the way, a very interesting comment was made by a dear friend of mine and ardent lover of history, who asked me what would be the case with "othismos" and the Iphicratean hoplites. As we all, most probably, know, sometime in the 4th century BC, Iphicrates changed the armament of his hoplites giving them lighter armor, a smaller shield and a longer spear. They were also called "peltasts" and could still fight as hoplites. Would they perform "othismos"? If "othismos" was such a devastatingly important tactic, then why did Iphicrates reduce the hoplon size?

I think Iphicratids were specifically designed not to enter othismos, but to match hoplites at doratismos- the longer spears and swords make sense in a the context of avoiding close fighting. That this was insufficient can be shown that these troops did not last long after their initial "success". Iphictates wanted troops that could keep up with his peltasts and yet have enough punch to hit a phalanx. Recall outside Corinth, his peltasts essentially beat the hoplites they attacked and yet were not able to close the deal because they could not come to grips with them. A squad of hoplites was required to eventually break the enemy phalanx.

If "iphicratids" were willing to give ground before a phalanx, and not even all that much ground, there could never be an "othismos". An iphicratid could do all the pre-othismos pushing just as well as a hoplite. Perhaps better if as I suspect he carried an oval, single-central grip pelta like those seen in Thrace, which could be "punched" with. The weakness is that giving ground is always something to be avoided and takes great training to pull off.