[2] After Romania entered World War II on the side of the Axis in June 1941, Constantinescu-Claps commanded the XI Corps from July 18, 1941, during Operation Barbarossa.

On November 9, 1941, Constantinescu-Claps was appointed the commander of the Romanian Fourth Army and was promoted to lieutenant general in January 1942.

Most of these formations were in deplorable shape, with at best 73% of necessary manpower, with the 1st Infantry Division going as low as 25% and an almost nonexistent arsenal of heavy antitank guns.

[4] The 4th Army occupied a line running approximately 170 miles (270 km) from Staraya Otrada to Sarpa, which provided the perfect spot for Marshal Georgy Zhukov's southern strike at the start of Operation Uranus.

In spite of his rank and unlike many other Romanian generals, he never received any German medals and was in conflict with Conducător Ion Antonescu.

[8] He was married to Henrietta, née Răileanu, a descendant on her mother's side of the Sturdza and Rosetti families; the two had a son, Radu Constantinescu (1919–1998).