He was born in Beceni, Bacău County in 1884. From 1903 to 1905 he attended the Military School of Artillery and Genius, graduating with the rank of second lieutenant, advancing to lieutenant in 1909 and captain in 1913. During the Second Balkan War and the Romanian Campaign of World War I he served with the 12th Artillery Regiment. He fought in the Battle of Transylvania in 1916 and the battle of Măgura Cașin in 1917. For his valor, he was promoted to major in 1917 and was awarded in 1917 the Order of the Crown, Knight rank. After the war, Constantinescu-Claps was promoted to lieutenant colonel in 1919, and attended the Higher War School in 1919–1920.