In this period the design of fortifications was based on the bastion "trace" or ground-plan. This had originated in Italy in the 16th century. From the late 17th century the model system of fortification was considered to be that based on the bastion trace of Vauban, Louis XIV's military engineer. Carnot opposed the Bastion system. The elements of his system were: * vertical fire from mortars; * a countersloping glacis; * sorties by defenders; * the "Carnot" wall and; * separation of defence and attack.