As early as the fourteenth century, with the firm establishment of the Saxon farming system on the Continent and in the crop-growing areas of England, the sheep tending dog became an essential tool in the service of agriculture.
Each Saxon manor was an extensive holding that included lands that would produce most of the necessities of life: woodlands, orchards, vineyards, waterways, market roads, grain fields and vegetable patches. There was no fencing around any part of the manor before the 1800s in England and in Germany, there is still not much fencing in the intensive agricultural areas. Therefore, in modern Germany, there is still a need for a sheep tending dog that serves the same purposes as the dogs of medieval times, namely: to provide a "living fence" to control the column of sheep as it follows the shepherd through open countryside and to hold the sheep on their assigned grazing area and to ward them off the nearby crops.
The Saxon manor farming system required that a certain number of vegetable or grain-growing patches lie fallow (unplanted) each season. The fallow patch of ground supported stubble in late Summer and grass grew on it the following Spring. The stubble and grass were the only legal forage that the farm provided for the sheep. The tending dog took his sheep through the actively growing vegetable and grain patches without the sheep pilfering snacks as they passed. The dog actively patrolled the narrow column of a few hundred sheep and then settled them on the fallow plot. Nowadays, the herd is up nearer a thousand head, a real handful for two dogs.
We know the approximate size of most of those Saxon farm plots or patches, because we still have a unit of measure in modern English which relates to their size: furlong. A furlong is the length that a draft animal can pull a heavy plow in a straight line without needing to stop, turn and relieve stress from his yoke. The modern equivalent of a furlong is ~220 yards, about a 10-acre parcel.
These 10-acre parcels usually had a furrow running along two or three sides if not all four sides. Here is where the dog could work without pressuring the sheep and without damaging the crops in the adjacent patch. From about the 1500s until the late 1800s, thousands of dogs worked the borders of those fallow fields throughout Europe (and in Germany, in particular), developing into a specialized branch of the canine family.
Although the foregoing describes a German farming system which also operated in England until the Enclosure Acts in the 1800s, the work did not require a specific breed or national origin for the working dogs. If one studies nineteenth century photographs of sheep tending dogs in Germany, or if one observes the modern herding dogs of Germany, he will see dogs that look like American "Aussies," Border Collies, Bernese Mountain Dogs, Briards, Poodles, Schnauzers, Belgian Shepherds, Bouviers, and of course, like the twentieth century German Shepherd Dog. Before the 1890s, all these dogs were called German Shepherd Dogs if they worked sheep in Germany. The dogs that are not bred to a standard are now called Old German Shepherd Dogs (Altdeutscher Schaeferhund) and those that are bred to the breed standard are known as the German Shepherd Dog (Deutscher Schaeferhund).
However, even today, most herding dogs in Germany are bred for working ability only, and therefore a great many of 5000 or so sheep tending dogs presently working are "generic" in appearance. They may be called Old German Shepherd Dogs because they herd sheep in Germany, but they may look like any or all of the breeds mentioned above. As a result, we find that the sheep tending instinct is not isolated only in the genes of the breed that is called German Shepherds here in America, but is often manifest in many of the modern standard breeds named above. Blessedly, that deep-rooted instinct does appear with great frequency in the modern standard German Shepherd Dog.