Ancient methods for harnessing horses did not allow the full utilization of the horse's power.

Classical Harness

This surprising fact was first noted by Richard Lefebvre des Noëttes, who, as late as 1931 pointed out that the classical harness involved placing a strap around the horse's neck against which the horse pulled. [Richard Lefebvre des Noëttes, L'Attelage et le cheval de selle à travers les âges (Paris, A. Picard, 1931)] This limited the load the horse could pull without being put into distress, because, as Lefebvre des Noëttes put it, "This collar compresses the trachea and impedes respiration." (Lefebvre des Noëttes, Volume I, page 162.) This view was accepted for years, though recently questions have been raised concerning just how much difficulty the Roman harness actually imposed on the horse. This is discussed in a separate article.

The breast-strap came into use by the 6th century in Germany.

Breast Strap Harness

[White 1962. p. 61] This harnessing technique moved the load-point to the horse's chest, thus removing the stress on the neck and allowing the horse to develop much greater power. Nevertheless, the breast strap was not a perfect solution as it tended to ride up to the neck under pressure from a load attached high on the back. To counter this the breast strap was held down by another strap that passed from it, between the front legs of the horse, and then to a girth strap. In addition, the load was attached to the breast band as low as possible. All of this served to allow the chest, rather than the neck, to be the contact between the horse and the load. [Derry and Williams 1960. p 201]

 

Medieval Harness

The breast-strap was followed a few centuries later by the introduction of the horse collar. The horse collar seems first to have been used in Europe around the 8th or 9th century [White, p. 61]. This may have been a northern European development or, as both White [White 1962. p 61] and Usher [Usher 1954. p 183] suggest, imported from the east. The horse collar rests on both the shoulders and the breast of the horse. The traces and thus the traction points, are over the horse's shoulders, not high on the horse's back. This allows the horse to develop much more power without putting any pressure on its neck.

 

Harrow pulled by horse in horsecollar (Très Riches Heures du Duc de Berry)

Use of the horse collar seems to have spread rapidly though not uniformly through European agriculture and heavy freight hauling -- though in neither case did the use of oxen ever totally vanish. [Langdon 1986. pp 19-20] Oxen were cheaper than horses, but horses are 50% faster than oxen and can work more hours during the day. But they were no stronger than oxen in total pulling force, were more difficult to care for, and required specialized (and more expensive) food. Nevertheless, by the late Middle Ages the use of the horse in agriculture became very common. [Gimpel 1976. p 35]

 

Transport of rubble Original illustration from The Bern Chronicle of 1484-5 by Diebold Schilling

By the late Middle Ages horses were commonly used in heavy hauling in many regions. [Raepsaet 1997 p 58] [Comet 1997 p. 20-21] In the picture to the right (from 1484-5), horses are seen hauling rubble to a building site. The load being hauled by the single horse in the foreground would seem to approximate one ton, although it is impossible to be accurate. The picture illustrates two harnessing methods, both involving the horsecollar. In the foreground the horse is harnessed to the cart by two rigid drawpoles attached to the cart and to the collar, low down at the horses chest. In the background a team of horses is attached to a cart using a whippletree and chains, again attached to the collar low down on the horses chest.