The Makedonian phalanx -- why such depth?

[Giannis K. Hoplite]

In fact,hypaspist is an earlier word that meant "servant", the one who carries your shield untill you're about to fight. They were not a unit. It s more likely that the macedonian hypaspist took their name from their service under the king himself than from the usage of any particular kind of shield. For one,the hypaspist were a unit trained to fight in different ways.
Khaire
Giannis