How did Alexander accomplish the goal his father was unable to reach?

Alexander the great accomplished the goal of uniting and expanding the Greek city-states into a vast empire, something his father, King Philip II of Macedonia, could not fully achieve due to his assassination. Alexander built upon his father's military reforms and diplomatic strategies, successfully leading a campaign against Persia that extended his empire across three continents. His exceptional leadership, tactical brilliance, and ability to inspire loyalty among his troops enabled him to conquer territories that had eluded his father. Ultimately, Alexander's ambition and vision for a unified empire transcended the limitations faced by Philip.