Horses
In peacetime, horses could carry trade goods
from one city to another, and they could pull wagons full of people or hay
or wheat or pots
from one place to another too.
Horses were not much used for plowing in the ancient world, where oxen were generally used instead. Horses were too expensive, and they needed better quality food than oxen. Also, no good harness arrangement for horses was invented until about 200 BC, when one was invented in China.
Ucello horses
Also, until the medieval period, men generally did not really fight on horseback. They rode their horses to the battle and then dismounted to fight. In the Middle Ages this changed with the development of mounted knights. Some people have said that this was because the stirrup had not been invented until the Middle Ages, but this is probably not the main reason.
More likely, the reason men did not fight on horseback under Greek and Roman rule is that horsemen are not actually that effective against trained, organized foot soldiers. Both the Greeks (after about 750 BC) and the Romans had trained footsoldiers, but in the medieval period armies did not have the resources to train footsoldiers, and so the cavalry (the horses and their riders) became more useful.
For more about horses, check out these books from Amazon.com or from your library:
Eyewitness: Horse, by Juliet Clutton-Brock (2000). For kids, with lots of pictures.
The Horse in the Ancient World, by Ann Hyland (2003). Mostly Greece and Rome.
Imperial China: The Art of the Horse in Chinese History, by Bill Cooke (2000). This is the catalogue of an art exhibit, so it has lovely pictures of everything to do with horses in imperial China. It has a lot of information about the history of horses in China, too.
