Sparta remained independent, but it was no longer the leading military power in the Peloponnese. The Spartan king Cleomenes III (235–222 BCE) staged a military coup against the conservative ephors and pushed through radical social and land reforms in order to increase the size of the shrinking Spartan citizenry able to provide military service and restore Spartan power. Sparta's bid for supremacy was crushed at the Battle of Sellasia (222) by the Achaean league and Macedon, who restored the power of the ephors.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): In 222 BCE, Sparta lost what Battle?
Battle of Sellasia