The Makedonian phalanx -- why such depth?

[PMBardunias]

Lazenby hypothesised that in fact the 'folding back'( anastrophe) involved moving troops from the un-engaged left of the Spartan contingent to the right for this purpose, so that Cleombrotos was attempting what Agis at Mantinea attempted, and perhaps the Spartans were also trying to increase their depth. It is hard to discern exactly what the Spartans were attempting to do, because they never got to complete their manouevre thanks to Pelopidas charging and disrupting it, and Cleombrotos didn't survive to explain.....

I'm with Paul on this one, Xenophon is perhaps our best source for much of this period- You'd prefer Ephorus??? He just has to be understood in context, and often we don't have the knowledge to do that since he leaves out so many details that are obvious to a man of his day.