§ 21. my own namesake: i.e. Demosthenes, who was a distinguished general during the Peloponnesian War, and perished in the Sicilian expedition.
§ 24. for forty-five years: i.e. between the Persian and Peloponnesian Wars, 476-431 B.C.
the king: i.e. Perdiccas II, who, however, took the side of Sparta shortly after the beginning of the Peloponnesian War. He died in 413. (The date of the beginning of his reign is unknown, but he did not become sole king of the whole of Macedonia until 436.)
§ 27. Spartans had been ruined: sc. by the battles of Leuctra (in 371) and Mantineia (in 362).
Thebans had their hands full, owing to the war with the Phocians, from 356 onwards.
§ 28. in the war, when Athens joined Thebes against Sparta (in 378). 'The allies' are those members of the Second Delian League (formed in 378) who had been lost in the Social War which ended in or about 355, when Athens was at peace with Thebes and Sparta. (See Introduction, vol. i, p. 9.)
§ 31. procession at the Boedromia. The Boedromia was a festival held in September in honour of Apollo and Artemis Agrotera, Probably a procession was not a regular part of the festival at this time. The importance which the populace attached to such processions is illustrated by the Speech against Timocrates, § 161.
§ 34. is it then paid service, &c.: almost, 'do you then suggest that we should earn our money?'
§ 35. adding or subtracting: sc. from the sums dispensed by the State to the citizens.
somebody's mercenaries. The reference is probably to the successes of Charidemus when first sent (see Introd. to Olynthiacs).