The Grenztruppen were the primary force guarding the Berlin Wall and the Inner German border, the GDR's international borders between West Berlin and West Germany respectively. The force belonged to the Ministry of National Defence (MfNV) from 1961, and was a service branch of the National People's Army until 1971 when it became directly subordinate to the MfNV. The Border Troops numbered approximately 47,000 personnel at its peak, consisting of volunteers and conscripts, the third-largest Warsaw Pact border guard after Soviet Union and Poland.