Some of the early Russian fortresses are superb historical monuments ranking as the world's best achievements in architecture. Their style, always explicit and individual, is reminiscent of the romantic exploits of the past. It is something that incarnates the heroism and courage of the Russian people, their love for the country and an immense effort dedicated to its defence and safe-guarding its interests.
If you look at the stone-built stronghold of Izborsk, a reliable frontier guard of the Free City of Pskov called by the enemies "the iron town" for its impregnability, you will be overwhelmed by its stern laconic aspect. Similar features can be discerned in the fortifications of Porkhov and Koporye, outposts of Novgorod the Great, which lived through many destructive assaults. Looking at the walls and towers of the Moscow Kremlin, the head fortress of the Russian State which emerged as an international power during the reign of Ivan the Third, one gets the impression of an immense power, eternal and indestructible. The Smolensk Citadel which the Russians used to call "the invincible stronghold of the Motherland", strikes you by its magnitude and originality. Like fairy castles rise from the earth the walls and turrets of the Solovetsky, Trinity-Sergius and Kirillo-Byelozyorsky Monasteries, "the great royal strongholds" which in a marvellous way combine the perfection of building work and an inimitable beauty.
The art of fortified construction in Russia underwent a long and complicated evolution. At any given period its progress was dependent on the productive forces of the country, the prevailing tactics of the enemy, the power of the siege-weapons being in use and the general achievements of building art and architecture. These were the main forces governing the development of Russian fortress architecture which was an important field of architecture in early Russia.
The first fortresses built in Russia in the 8th-10th centuries were of moderate size, their layout being fully subordinated to the terrain. The open approaches were protected by a rampart and a moat. The system of defences was localized on one side. It could deal with sudden enemy assaults but didn't meet the requirements of a long-time defence.
In the 10th-12th centuries, when the most effective way of capturing towns was a regular siege, new types of fortresses began to appear in Russia. Their defences consisted of ramparts which were raised on different solid foundations and of wooden walls of different structure standing on the ramparts. These fortresses were also built with due consideration of the terrain, but their defences ran the whole length of their perimeter, so that the garrison could carry on frontal fire in every direction.
The transition from passive sieges to direct assaults of fortified positions and the use of projecting machines brought about in the 13th century new qualitative changes in fortress architecture of early Russia. In the late 13th and the early 14th centuries, there appeared fortresses provided with a single tower, and later in the 14th century, fortresses with several defensive towers on the most vulnerable side. This was important for the subsequent development of
Russian fortress architecture. The defence of fortresses which was formerly passive began to acquire active elements. Active defence was organized in those directions where there were far-advanced towers standing close to one another and protected by artificial obstacles - ramparts and moats, while passive defence was held on the sides protected by walls without towers and such serious natural obstacles as rivers and steep hillsides.
The architectural view of fortresses with towers located on one side was stern but expressive. Its important elements were towers which had become the centres of defence. They had set in greater relief the assault walls of the fortresses, emphasizing the defensive power of these main facades. It was the majestic and expressive aspect of such facades that usually gave a Russian fortress its artistic quality.
In the second half of the 15th century artillery became the most effective means of destructing fortresses. Natural barriers ceased to be serious obstacles for the besiegers. They assaulted fortresses from all sides irrespective of these barriers. For this reason fortresses with towers concentrated on one side were superseded by fortresses in which towers were provided all along the perimeter of the walls. In the same period the spans between towers were straightened out. It was done in order to liquidate dead areas in front of the walls and make them open for flanking fire from towers. As a result the layout and the spacial organization of Russian fortresses were changed. Their defence system was no longer divided into active and passive. It was built so as to offer an active resistance in whatever direction the enemy would choose to attack.
The logical result of this general evolution was a kind of fortress with an absolutely correct, "regular" ground-plan and towers placed at corners. Such fortresses became very common in Russia in the 16th century. Fortified centres, multiangular in ground-plan, were also built in those times. They possessed all the advantages of "regular" fortresses. The frontal fire which was opened from the walls of such defensive fortifications crossed with the flanking fire from the towers, thus covering the entire space in front of the walls.
The architectural style of defensive constructions had also changed by that time. Architects began to provide the walls and turrets with modest decorative details which somewhat mitigated their severity, made them more colourful and picturesque. As a result, fortresses began to express the beauty and sublimity of the town rather than its military strength.
In the 17th century the principles of defensive organization of fortresses remained unchanged, though the tradition of defence construction was maintained mostly by monasteries which were the centres of cultural and economic activities in areas with scarce population and the outposts of defence of the state in most strategic points. Though the massive walls and towers of the monasteries were designed for defence, great importance was also attached to their architectural and aesthetic qualities. The subject of special attention of the architects were the defence towers. In some monasteries each tower by its general proportions and outside ornamentation was an independent construction. It often happened that towers of one monastery were absolutely different in style and did not resemble one another in the least. Some of them were distinguishable in the ensemble of the other monastery towers due to their graceful and refined forms. All this led to a situation when defensive works which formerly had had only functional importance acquired a decorative role. Their aesthetic qualities had become more important than their practical usefulness.
By the beginning of the 18th century fortress architecture ceased to exist. It gave way to a new branch of military engineering - permanent fortification, which was not the field of an architect and a civil engineer, but of a specially trained military fortifier.