A fortress is a fortress that had separate fortifications ahead of the fortress - forts . Before the fort system appeared, bastion and polygonal systems were used, which implied a solid front of fortification.
The idea of a fortress was first theoretically substantiated by a military engineer M.R. Moptalamber at the end of the 18th century. However, the first practical implementation of F. to. Was implemented much earlier than Montalamber by Peter I in Kronstadt , where, according to his plan, a fortress was built, consisting of a nucleus and separate advanced forts in front of it. The same idea was laid down by Peter I in the strengthening of St. Petersburg. It is suggested that Montalamber saw his fortifications during his stay in Petersburg, and from here he got the idea of a fortress.
With the advent of mass armies and increased range of artillery, a new type of fortress was developed with two forward belts of forts carried forward and reinforced by the gaps between them.