Firdawsi composed the Shah Nama (Book of Kings), an epic poem of 50,000 verses, in the late tenth century. Based on oral traditions that went back hundreds of years to the ancient Sassanian kings, this national epic is still familiar to most Iranians. King Khusrau is the main hero of the story, though the exploits of Alexander the Great (Iskandar) and King Bahram Gur are also described. The manuscript recounts numerous historical and biographical episodes that illustrate the righteousness and moral power of these pre-Islamic rulers.