The Iron Horsemen Filled with Naphtha

From D5.14, Iskandar Makes Iron Steeds Filled with Naphtha. It illustrates D5.14.52–59:

D5.14.52
They forged both horse and rider, iron-bright;An iron saddle bore the man upright.
D5.14.53
With nails and copper binding every seam,They made both horse and rider shine and gleam.
D5.14.54
They wheeled it to the king upon a cart,Black naphtha filling all its hollow heart.
D5.14.55
The king beheld the work with great delight;He judged the craft would serve him in the fight.
D5.14.56
He ordered more than one full thousand made,Both horse and rider, all in iron arrayed.
D5.14.57
Dappled and dun, gray, black, the ranks appeared;Who ever saw an iron army reared?
D5.14.58
For one full month the smithies rang with blows,Till all the finished figures stood in rows.
D5.14.59
He sent the iron force on wheels to ride,Like fighting horsemen marching side by side.