Hammarskiöld was born on 26 June 1869 in Dingtuna Parish, Västmanland County, Sweden, the son of major Per Theodor Hammarskiöld and his wife Sofia Gustafva Regnell. He was grandnephew of Lorenzo Hammarsköld. He was commissioned as an officer in First Svea Artillery Regiment in 1889 with the rank of underlöjtnant. Hammarskiöld attended the Artillery and Engineering College from 1893 to 1897 and served as a dispatch officer in staff of the IV Army Division in 1898. He became an artillery staff officer in 1899 and was secretary in artillery commissions from 1900 to 1902 and was promoted to captain in 1903. He participated in the work of the Boden Committee in 1905 and served in the General Staff from 1908 to 1909 and became major in the army and chief of the Artillery Staff in 1909. He then served as major in Svea Artillery Regiment in 1911 and as lieutenant colonel in Boden-Karlsborg Artillery Regiment in 1913. Hammarskiöld served as chairman of the Artillery Committee from 1914 to 1915. Hammarskiöld was promoted to colonel in 1915 and was appointed regimental commander of Småland Artillery Regiment in Jönköping. He was a member of the committee for the preparation of a stalemate warfare instruction from 1916 to 1917 and a member of the study commission to the German Army and the Eastern Front from 1916 to 1917. Hammarskiöld was commanding officer of the Swedish Army Artillery School from 1919 to 1920 and of Svea Artillery Regiment from 1922 to 1926. Hammarskiöld was chairman of the Artillery Committee from 1922 to 1923 and a member of the Army Council in 1923 and in 1925. In 1926, Hammarskiöld was promoted to major general and appointed commanding officer of the 2nd Army Division. Hammarskiöld was commanding officer of the Eastern Army Division and Commandant General of Stockholm Garrison from 1928 to 1929 and was then appointed Master-General of the Ordnance and Inspector of the Artillery in 1929. He was promoted to lieutenant general in 1933 and retired and transferred to the reserve in 1934. Hammarskiöld had strong military history interests. After entering retirement he devoted himself to thorough research on the Swedish artillery in the past. He dealt with topics such as De äldre Vasakungarnas artilleri , Artilleriet under Gustaf II Adolfs krig and Artilleriet i slaget vid Jankow den 24 febr 1645 , published in Artilleri-tidskrift. In 1922 he published Studie över artilleriets samverkan med infanteriet.
Personal life
Hammarskiöld married on 22 July 1896 in Hedvig Eleonora Parish, Stockholm to Gerda Cecilia Neijber, the daughter of Magnus Julius Neijber and Augusta Henriette Moll. He was the father five children: Karin Augusta Sofia Hammarskjöld, a businesswoman, Per Arvid Magnus Hammarskiöld, an engineer, Sven Ludvig Hammarskiöld, a judge and businessman, Göran Hammarskjöld, an officer, and Lennart Hammarskiöld, a banker. Hammarskiöld died on 4 July 1958 in Engelbrekt Parish, Stockholm. He was buried on 25 August 1958 in a family grave in Norra begravningsplatsen in Solna Municipality.
