In the 15th century, the shape of these things gradually changed from circular to star-shaped.  
Menno van Coehoorn laid down "New" ideas for constructing these things in a 1685 text.  Van Coehoorn was called the "Hollandish" version of a Frenchman and bayonet inventor best known for constructing these things.  Twelve constructions of this type, now classified as UNESCO World Heritage sites, were built during the reign of Louis XIV by (*) Vauban.  Some of these things might have a slight slope near them called a glacis.  Geoffrey Parker connected the rise of a new type of these things called trace italienne to the 16th century military revolution.  In the 15th century, the shape of these things gradually changed from circular to star-shaped.  French examples of these things often had several ravelins in front of their curtains.  For 10 points, name these defensive structures, examples of which include Louisburg in Nova Scotia.
Menno van Coehoorn laid down "New" ideas for constructing these things in a 1685 text.  
fortresses [or forts or fortifications or castles]