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Note the horse collar.
Scholars pretty much agree that the development of the heavy plow (mouldboard plow) was essential to the economic rise of Medieval Europe. It replaced the scratch plow (ard plow) used widely in Southern Europe. The heavy plow became common in Northern Europe between 900 and 1300. Increased cultivation led to the growth of population, cities, and trade. The development of padded horse collars made horses more practical for plowing.
To learn more about the heavy plow:
http://sciencenordic.com/how-heavy-plough-changed-world
To learn about horse collars:
My medieval novels are available on Amazon:
thegraceofironclothing 