In the Spring of 334 BC, the 22-year-old Macedonian king, Alexander III (r. 336-323 BC - not yet 'the Great'), invaded the vast Achaemenid Persian Empire with an elite but small army of some 30-40,000 veteran infantry and only 5,000 cavalry. This invasion was the culmination of almost a century of pressure for some Greek commander or other to punish Persia for its own invasion of Greece during the fifth century BC. Persia had also continued to seriously meddle in Greek affairs thereafter, affecting the end of the Peloponnesian War in 404 BC and with the King's Peace in 386 BC. Dur: 31mins File: .mp3