When Sumerians used these in war, they had 4 wheels & were drawn by big-eared equines called onagers
[DOC] [TLE] The Opening of the Eurasian Steppes - The Horse, the Wheel, and ... [PAR] They did not use horse-drawn chariots, which had not yet appeared in Near 
Eastern ... Ass-onager hybrids probably pulled Sumerian battle carts and battle 
wagons.