The Makedonian phalanx -- why such depth?

[Macedon]

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?

Maybe we should open a new thread about othismos, since we seem to carry out two different discussions here...