It is often cited as an argument for the indispensability of horseshoes by their supporters that horseshoes have been in use for thousands of years for riding and draft horses. According to the the most recent findings, however, it is certain that the horseshoe was first introduced to Western and Central Europe in the 9th Century, and was previously completely unknown.
In Ancient Greece, too, the riding horses went barefoot. The Greek Xenophon began his treatise "On the Art of Riding" (written about 400 BC) with horses' hooves, and emphasised the great importance of regular hoofcare. His book deals exclusively with the husbandry and training of military horses, which could perform their duties very well without shoes. Markus Junkelmann writes in his book "The Riders of Rome" (Die Reiter Roms vol.3) "The great distances covered by Scythian, Persian, Macedonian and Carthagian cavalries during their campaigns--think only of the battles of Alexander the Great--show that cavalry, even without horseshoes, is capable of the greatest of achievements." And what about the Ancient Romans' attitude to hoof protection? We know of the so-called "hippo sandal" of iron, "soleae ferreae" in Latin, which was in use in the Celtic-Roman area north of the Alps from the middle of the 1st century to the 4th Century AD. The hooves were wrapped and placed in the shoes, which were then fastened with the help of bands running through hooks and eyes at the front and back ends of the shoes. The hippo sandals were usually allowed to be worn only by draft and pack animals walking on "paved" roads, since a gait faster than the walk seems to have been impossible with the hippo sandals.
Nailed-on horseshoes are to be found neither in Roman literature, nor depicted in art. The equestrian statue of Caesar Marcus Aurelius (died 180AD) shows a horse with beautiful natural hooves. Since the sculptor represented every detail of the horse and rider very realistically and accurately, he certainly would not have simply left out a form of hoof protection. But no Roman work of art shows even a single shod hoof, while in the Middle Ages shod hooves are always clearly shown even in simple pictures. There are various medieval paintings in which the artist has faithfully represented the shod hooves as contracted hooves--as contracted hooves are in fact a consequence of shoeing.