So the Persian Achaemenid dynasty, Achaemenid? Hold on. Achaemenid or Achaemenid? They're both right? I was right twice? Right, so the Persian Achaemenid or Achaemenid dynasty was founded in 539 BCE by King Cyrus the Great. Cyrus took his nomadic warriors and conquered most of Mesopotamia, including the Babylonians, which ended a sad period in Jewish history called the Babylonian Exile, thus ensuring that Cyrus got great press in the Bible.