Soon after the victory of the October Socialist Revolution, organs of Soviet power began to implement special measures for the preservation of the Peter and Paul Fortress as a historical and architectural complex.
Prior to the Revolution the Sts Peter and Paul Cathedral was considered the main attraction on Fortress Island. In the summer of 1917 the cathedral suffered the fate of many other Petrograd museums and historical buildings: by order of the Provisional Government, considering the threat of approaching German forces, all of the items hand-made by Peter I, together with manuscripts and books published in Russia before the eighteenth century, the most valuable icons and ecclesiastical vestments were evacuated from the cathedral and transferred to Moscow. The Provisional Government delegated the preservation of the cathedral itself, as well as the Grand Ducal Burial Vault and the house in which Peter the Great’s boat was kept, to the cathedral’s resident clergy.
Less than two years after the Revolution organs of Soviet power took on the preservation of these buildings. On May 27, 1919, when the spring campaign was launched against Petrograd by the White Army, the buildings were examined and sealed by a special state commission. Its members insisted that a protective zone be created around the entire fortress. Emphasizing in their report that the Peter and Paul Fortress represents “a monument of great historical and cultural value”, they further stated: “The silhouette of the cathedral together with the fortress constitutes the main and most characteristic landmark of the Petrograd skyline, without which the city would not be quite the same. Therefore, it is of the utmost importance that in the future this silhouette be preserved, and in so doing attention should be given to all those structures erected or reconstructed inside the fortress as well as those nearby, for any change will disrupt that wonderful harmony which is created by the horizontal lines of the fortress and the sharp vertical lines of the cathedral’s spire.” The members of the commission insisted on immediately placing the cathedral and Boathouse under special legal protective status. On September 24, 1919, because of the autumn campaign launched on Petrograd by the White Army, military authorities were required to take the entire Peter and Paul Fortress under their control, making it the centre of the city’s internal defence. Nevertheless, city officials continued to emphasize the necessity of the preservation of the historical structures on Fortress Island. In spite of the extremely short supply of firewood in Petrograd (practically the only available source of heat in the city) during the Civil War, provisions were made for the regular heating of the cathedral so that this outstanding architectural monument would be safe from dampness.
The Sts Peter and Paul Cathedral attracted popular interest from the very start of Soviet power. As early as 1918 the question of organizing tours of Fortress Island was being discussed. However, it was impossible to grant broad access to visitors to view its historical and cultural sights until December 3, 1920, the end of the Civil War and the date when the state of siege was officially lifted in Petrograd. Thereafter, in July 1920, the first excursion group made an official tour of the fortress, a group consisting of delegates of the Second Congress of the Third International. Tours of the fortress commenced on a regular basis beginning in the summer of 1922. The end of the war allowed more effective measures to be taken for the preservation of the whole fortress as a complex of architectural and historical monuments. The Tru-betskoi Bastion and the prison facilities within it, closely tied to the history of the Russian revolutionary movement, became one of the main attractions of the fortress. In 1923, by order of the highest military authorities, the bastion and prison were made part of the Museum of the Revolution. In the same year allocations were made for the first restoration work to be carried out during Soviet times on the Sts Peter and Paul Cathedral, and a custodian-architect was assigned to maintain it.
In 1924 specialists began work on restoration of the cathedral interior, keeping in mind that the cathedral is not only an architectural landmark, but a historical monument as well. However, restoration of just the cathedral and prison facilities in the Trubetskoi Bastion was not enough to make the entire fortress accessible to the inhabitants and visitors of Leningrad. Therefore, in the period from 1925 to 1927 large-scale improvements were made on Fortress Island: roads and lawns were layed out; new bushes and trees were planted, and its banks were reinforced. The decision was made at this time to restore the grate of the batardeau on the eastern end of the island, which had been removed in 1892. True, the major part of the fortress still remained under the command of the military – in the first decades following the Revolution Leningrad was essentially a border city. However, both military and municipal authorities understood that in the future the entire fortress should become an object of special care and use, namely as a museum-citadel. The only remaining building of a non-museum nature that was to remain was the Mint Works (it had been partially dismantled in 1918, but already in 1921 had resumed production). During the 1920s and 1930s much was done for the preservation of the Peter and Paul Fortress by the volunteer scientific society “Old Petersburg – New Leningrad”, among whose main tasks it was to facilitate the best use of historical and architectural monuments of St Petersburg under the new conditions of the socialist reconstruction of Leningrad. During the siege of Leningrad by Nazi forces, lasting from September 8, 1941, to January 27, 1944, everything possible was done in order to save the historical and architectural monuments of the fortress, which were once again under command of Soviet military authorities. The gilt spire of the Sts Peter and Paul Cathedral was camouflaged. In December 1942 soldiers of the local air defence force completed work to protect the cathedral from the destructive effects of dampness, repairing the roof which had been damaged by shell fragments and sealing the windows, in which almost no glass remained.