We have significant amounts written by the Ancient Greek equivalent of a Sparta otaku, Thucydides. He lived there for a significant period (IIRC, he was in exile from Athens at the time) and was firsthand familiar.

An example of the orderly battle of the hellens from Xenophons Anabasis where the enemy has ten-fold numeric superiority:

Clearchus, though he could see the compact body at the centre, and had been told by Cyrus that the king lay outside the Hellenic left (for, owing to numerical superiority, the king, while holding his own centre, could well overlap Cyrus's extreme left), still hesitated to draw off his right wing from the river, for fear of being turned on both flanks; and he simply replied, assuring Cyrus that he would take care all went well.

...

At this time the barbarian army was evenly advancing, and the Hellenic division was still riveted to the spot, completing its formation as the various contingents came up.

...

And now the two battle lines were no more than three or four furlongs apart, when the Hellenes began chanting the paean, and at the same time advanced against the enemy. But with the forward movement a certain portion of the line curved onwards in advance, with wave-like sinuosity, and the portion left behind quickened to a run; and simultaneously a thrilling cry burst from all lips, like that in honour of the war-god—eleleu! eleleu! and the running became general. Some say they clashed their shields and spears, thereby causing terror to the horses (4); and before they had got within arrowshot the barbarians swerved and took to flight. And now the Hellenes gave chase with might and main, checked only by shouts to one another not to race, but to keep their ranks. The enemy's chariots, reft of their charioteers, swept onwards, some through the enemy themselves, others past the Hellenes. They, as they saw them coming, opened a gap and let them pass. One fellow, like some dumbfoundered mortal on a racecourse, was caught by the heels, but even he, they said, received no hurt, nor indeed, with the single exception of some one on the left wing who was said to have been wounded by an arrow, did any Hellene in this battle suffer a single hurt.