Others attribute the invention to Ziska, the celebrated leader of the Hussites.

It is most probable that the transition from the tower to the bastion was a very gradual one, and that the change was perfected in several countries at about the same time.
Fortifications, like other arts and sciences, greatly flourished in Italy under the Medicis, and that country furnished Europe with its most skilful engineers.

Catharine of Medicis introduced into France many of her countrymen, distinguished in this profession; among these may be named Bellamat, Bephano, Costritio, Relogio, Vorganno, the two Marini, Campi, and Hieronimo, who built several important places and directed the sieges of others.

These able foreigners were rivalled by some distinguished French engineers, who laid the foundation of the "_corps du Genie_" which has since become a school of military instruction for the world.

Among the early French engineers may be distinguished Lafontaine De Serre, Feuquieres, and St.Remy.Pedro Navarro had been appointed a member of this corps, but his attention was more specially directed to mining, and we do not learn that he distinguished himself in the construction of any fortification.
In Germany, in the beginning of the sixteenth century, Albert Durer distinguished himself as a writer on fortification; his book is remarkable as containing the germs of many of the improvements which were made by those who followed him.