The army of the Kingdom of Macedonia was among the greatest military forces of the ancient world. It was created and made formidable by King Philip II of Macedon; previously the army of Macedon had been of little account in the politics of the Greek world, and Macedonia had been regarded as a second-rate power. Unfortunately, most of the primary historical sources for this period have been lost. As a consequence, scholarship is largely reliant on the writings of Diodorus Siculus and Arrian, both of whom lived centuries later than the events they describe.