Fortress Study , Page 1 0f 2

Fortress Study -- The thirteen fortress  drawings (Sheet 1 & 2) are
a list of the defences erected in the Spanish Highlands by the British army
to either stop or delay the forces of Napolion during the Penninsular
Wars of the late 18th or early 19th centuries.  The artillery firing
angles and ranges intersected because most of these forts were so
constructed on hilltops, within cannon range of each other.