The Kingdom of Macedon possessed one of the most effective and successful armies in the ancient world. It became noted for its speed of movement and proficiency in combat. After gaining an ascendancy in Greece the army was instrumental in the conquest of large swathes of territory stretching from Egypt in the west to India in the east. Initially of little account in the Greek world, Macedon was widely regarded as a second-rate power before being made formidable by Philip II, whose son and successor, Alexander the Great, conquered the Achaemenid Empire in just over a decade.