The Arcadian army, after ravaging Elis in the spring of 364 BCE, marches against the little town Cromnus, in the neighborhood of Megalopolis, and lays siege to the city, in which Archidamus had left a small garrison.

The Arcadians defeat Archidamus's relief force.

The Boeotian league destroys Thebes' Boeotian rival Orchomenus in 364 BCE.

Epaminondas in this year commands a fleet against the Athenian navy and …

…Pelopidas marches against Alexander of Pherae, who, during the past three years, has seemed to renew his attempts to subdue the states of Thessaly, especially Magnesia and Phthiotis, for upon the expiry of the truce in 364 BCE they again apply to Thebes for protection from him.

The Theban army under Pelopidas is said to have been dismayed by an eclipse on July 13, 364, and Pelopidas, leaving the bulk of his army behind, enters Thessaly at the head of three hundred volunteer horsemen and some mercenaries.

At Cynoscephalae (Greek: “Dogs' Heads”), an ancient range of hills in Thessaly, the Thebans defeat Alexander, but Pelopidas is killed.

This is closely followed by another Theban victory under Malcites and Diogiton.

Alexander is now forced to restore the conquered towns to the Thessalians, confine himself to Pherae, join the Boeotian League, and become a dependent ally of Thebes.

The Thebans release the hostage prince Philip in 364 BCE also.

The Macedonian prince during his captivity has received a military and diplomatic education from Epaminondas, become the eromenos of Pelopidas, and lived with Pammenes, an enthusiastic advocate of the Sacred Band of Thebes.

The skills and techniques thus acquired are soon to prove valuable.

Amyntas, after a turbulent five-year interval of two brief reigns, those of Alexander II and Ptolemy, and one intervention by a pretender, Pausanias, had in 365 BCE been succeeded by Perdiccas, the second of his sons by Eurydice.

When Philip returns to Macedonia, his brother Perdiccas soon finds him ready for a command.

The fourth century Macedonian kings make grants of land in exchange for military service (a system hinted at by literary sources and illustrated by inscriptions).

Given the size and fertility of the areas controlled by the Macedonian kings, there is huge potential for military achievement, provided Macedon's chronic enemies and invaders can be appeased or crushed.

The immediate outcome of Cynoscephalae is favorable for Thebes and Thessaly is reorganized in a way that gives Thebes for the first time an absolute majority of votes on the Delphic Amphictyony, but active Theban interference in Thessaly is over.

Epaminondas in 364-363 BCE makes a bold attempt in 364-363 BCE to challenge Athens' naval empire.

Some naval interest on the part of Thebes can perhaps already be inferred from its designs on Thessaly, with its good harbors.

Theban rivalry with Athens had become explicit  after 365 BCE, however; Thebes plans a fleet of one hundred triremes, …

…lures away Athenian allies such as Rhodes and Byzantium, and …

…induces a revolt on Ceos.

This scheme is no more successful than the Thessalian entanglement: Athens will reduce the island in 362 and establish a monopoly of ruddle (red-earth dye), the island's principal product.

Athenian general Callistratus has supported Spartan interests at Athens, recognizing that Thebes poses the greater threat to Athens.

He had been one of the crafters of the peace treaty in 371 BCE between Athens and Sparta which recognized the hegemony of Athens on the sea and that of Sparta on land.

On account of the refusal of the Thebans to surrender Oropus, which on his advice they had been allowed to occupy temporarily, Callistratus had been impeached in 366 because of the failure of his policy to check Theban expansion.

He employs brilliant oratory to save himself from a death sentence.

Callistratus’ magnificent defense speech inspires a young spectator, Demosthenes—orphaned in 378 at age seven and given over to guardians who have misused his inheritance—to study the art of advocacy.

Demosthenes has practiced his delivery—according to legend, by putting pebbles in his mouth—and studied the masters of Athenian prose to perfect his skills.

Employing the exciting and explosive style he develops, he takes his guardians to court in 363 and wins his case.

The Boeotian League intervenes also in the Arcadian federation in the Peloponnese, which has split in two; the Tegean party appeals for help to the Thebans (who in turn have for allies the Argives and Messenians), and …

…the Mantineans to Athens and Sparta.

The outbreak of civil war in the Arcadian league in 362 brings Epaminondas once more to the head of a large allied army in the Peloponnese.

Leading the Boeotians and their Argive allies against Sparta, Athens, and their allies in an encounter on the Mantineian Plain, Epaminondas repeats on a large scale the tactics of Leuctra, cleverly outmaneuvering the Spartan troops, and is once more victorious but dies of a wound on the field of battle.

The great Battle of Mantinea (“Second Mantinea,” to distinguish it from the events of 418) is a technical victory for Thebes in the strictly military sense, but (as Xenophon notes) it is actually indecisive: Epaminondas' death permanently crushes Theban hopes of leadership in Greece.