The extraordinary openness of the urban world of the Northern Italian communes in the 12th century allowed the birth of a cavalry made up of anyone who wanted to join and could buy a horse. In the rest of Europe, it was a hereditary affair. A leader of this new cavalry was Master Guintelmo, a skilled craftsman and engineer. He would give rise to a veritable dynasty of engineers. They would design canals and ditches and war machines for military purposes in the service of Milan and Piacenza. These services would make the difference.
