With lockdown I have been researching around this battle and the general situation around it. There are numerous papers discussing all differing aspects of the campaign: Why did Sparta take such a large army against tiny Phocis? Were they so stupid as to not realise they could get cut off, and were they really cut off at all? Did their army include any Boeotion troops? Why did they camp at Tanagra? were they supporting Thebes? Did they always intend to fight the Athenians? No certain answers to any of these questions and more, but it was fun reading all the arguments.
Next I looked at the GMT GBoH Hoplite module scenario. Wall to wall MI hoplites whereas in GMT's Ancients version there are more light troops in both armies than hoplites. Weird?
The Historical discussion states that the Spartans won a victory that established their dominance on land for years to come, but it was hardly a victory at all. All they won was the right to bugger off home. The Athenians suffered no loss other than some face, and it could be argued that not getting stuffed by the Spartans was a moral victory. In fact after the Spartans had gone, and 62 days after the battle, Athens sent another army north and won a crushing victory against the Boeotians at Oenophyta not far from Tanagra, and this victory did establish Athenian dominance over Boeotia (Athenian land Empire) for the next 10 years.