By the time of Phillip and Alexander, Sparta had become something of a non-player. The Theban Democracy under Epaminondas had broken the Spartan Army at the Battle of Leuctra, invaded and ravaged Laconia, freed the Helots, setting them up in a mountain strong in Messenia formally part of Sparta. This effectively undermined the economic model that made the Spartan system work.

The League of Corinth that Phillip the II setup up after defeating Athens and Thebes, was about 40 years later. Phillip did not Annex much of Greece, rather he used the League as a way of levying troops without imposing direct control on their internal affairs. He also establish three garrisoned fortresses in order to maintain his influence on the peninsula, including one near Corinth controlling the isthmus to the Peloponnese.

Both Alexander and Phillip did not Campaign within the Peloponnese, and the new balance of power the Thebes had left their between the Messinians, Spartans Arcadians, Achaea and Argives had left plenty of space for the Macedonian kings to operate in diplomatically.

While Alexander was conquering Persia he sent spoils back to Greece with the note:

Alexander,son of Philip, and the Hellenes, except the Lacedaemonians, from the barbarians inhabiting Asia.

While on Campaign the Persians bribed Sparta to attack Alexander in the rear, but they were defeated, and forced into the League of Corinth by Antipater the general Alexander left behind in Greece as regent. While its true that Sparta was never conquered by Philip or Alexander, it was probably more its weakness and relative unimportance than anything else that saved it. It was only when Sparta acted against Macedon that it was swiftly brought to heel.