Historians highlight four periods of intense activities concerning guarding the eastern border of Poland, such as: 1921–1922 – a defense campaign conducted by both the Customs Battalions and the troops of the State Police 1922–1923 – the Border Guard responsible for maintaining border’s security 1923–1924 – eastern frontier under protection of the State Police 1924–1939 – the control of the border handed over to the Border Protection Corps (Korpus Ochrony Pogranicza, KOP). The decree passed by the Government on 13 January 1921 assigned the troops of “border militia” a task of providing the areas being a neutral zone with safety, peace and public order. On 18 March 1921 these troops were incorporated into the State Police corps. The Government’s instruction entrusted the Customs Battalions from 3 September 1921 with guarding the eastern border in the areas of Nowogródek, Polesie, Ternopil and Volhynia voivodships. In order to enforce their activities the State Police troops were ordered to support the Customs Battalions (BC). Soon, it turned out that in Volhynia, relations between the police and the BC were rather difficult. The Customs Battalions’ abuses leaded to many misunderstandings and furthermore to loss of contact and mutual agreement between the army and the police. In May 1922 the BC was replaced by the Border Guard which, in accordance with the relevant regulations, was obliged to cooperate with the State Police. The range of that cooperation included such activities as: prosecuting for criminal and political offences, patrolling the border, controlling documents and arresting those who were being thought as suspicious. Direct contacts between the police forces and the Border Guard were at border checkpoints as well as at border posts in Korets, Ostroh, Borshchiv, Szumsk and Mogilany. In the middle of 1921, in the area of Volhynia, it was organized the Control Station in Rivne which performed the function of the Branch Office of Department IV-D (Ekspozytura Wydziału IV-D). From 1 July 1923, the State Police (PP) – with 1300 police officers – took over from the Border Guard the control over the eastern border. Therefore the PP became responsible for controlling the movement of citizens, preventing smuggling by arresting suspicious individuals and sending them to the appropriate authorities and, in cases of reasonable suspicion of a contraband, by carrying out the revision of people and their properties located in the border zone, etc. On 1 November 1924, the Government recalled the police from the border zone in the area of Vilnus Region, Nowogródek and Volhynia voivodships. Defending of the eastern frontier was ordered to the Border Protection Corps which continued its mission until September 1939.