The article analyzes an issue of military and state secrets protection in 1943, year of radical change in the Great Patriotic War, in its interrelation with the course of fighting and the beginning of liberation of the occupied territories. The purpose and tasks of the article are identification and description of the measures taken for information security during that period, as well as of how the fighting impacted upon structure, contents and character of the classified information. The author mentions facts and describes measures taken by the Soviet state and refers to interaction of the supreme bodies of party, executive power and Glavlit on protection of military and state secrets in 1943. Also he presented a wide range of the classified information which protection became relevant in the course of fighting. Amount of the state and military information kept from disclosure leads to a conclusion that the arrangements in information security and existence of censorship were a necessary condition for a victory in the war. The Soviet state managed to prevent disclosure of a considerable part of the classified information of military and state value. The relevance and novelty of subject of the article are clear from the fact that it has not yet got the open press coverage. The article is entirely based on documents from the State Archive of the Russian Federation.