To eat the flesh of: it should be quite clear that these are dead bodies. The angel reads the menu:

Of kings … of captains … of mighty men: the captains are army officers; see in 6.15 “military chiefs” (Good News Bible); mighty men are soldiers, or warriors. It is not necessary, as Revised Standard Version does, to repeat the flesh of before each item.

The flesh of horses and their riders: this can be said “of horses and the soldiers who ride them.”

The flesh of all men, both free and slave: this includes everybody, slave or free. In English the order “slave and free” (Good News Translation) is more natural. For free and slave see 6.15.

Both small and great: see 11.18. Again, the order “great and small” (Good News Translation) is more natural in English.

For verses 17-18 see Ezek 39.17-20.

Quoted with permission from Bratcher, Robert G. and Hatton, Howard A. A Handbook on The Revelation to John. (UBS Handbook Series). New York: UBS, 1993. For this and other handbooks for translators see here .