Nicolescu was among the generals who prepared the King Michael's Coup of August 1944, and from November 1944 until the abolition of the monarchy in December 1947 served as head of the royal household. An adviser to King Michael I and palace marshal, he presented daily reports to the king regarding the situation on the front, commenting upon the course of the war. After the end of the war, he continued to brief the king regarding discussions within the higher army council, which debated laws and other measure touching on the military. In May 1946, the same year he was sent into the reserves, he joined the leadership of "Mișcărea Națională de Rezistență", an early group within the anti-communist resistance movement. Removed from the army in January 1948 by the new communist regime, he was arrested at the end of March. Later that year, he was sentenced to seven years' imprisonment for "plotting an uprising". His family was evicted from their home and persecuted. Part of his years in prison were spent at Jilava and Aiud. After being released in April 1955, he was not granted a pension and had to support himself by working on commission at an agency of "Loteria Română".