Johan Christian Sergei Fabritius (29 May 1890 â 2 November 1946) was a Finnish military lieutenant colonel.
He received his military training mainly in St. Petersburg and served during the First World War in the Russian engineering troops and participated in several battles in East Prussia, the Carpathians and Galicia. In 1917 he came to Finland and became chief of police in Rauma. In 1918, he commanded the White Guard on ÃÂ land and was later battalion commander in Satakunta.
In 1919 he was head of the fortifications department of the Ministry of War and from 1935 to 1938 acting head of the general staff's fortification department. He planned a large part of the fortifications that were built on the eastern border, Ladoga and the coast of the Gulf of Finland during the interwar period. That is why he has been called "the father of the Mannerheim line".
Fabritius was politically active in the Finnish-Swedish National Socialist circles before and during World War II. After Finland's armistice with the Soviet Union, in January 1945 he made a trip with a submarine to Germany. Lauri Törni was in same submarine. After negotiations with Ernst Kaltenbrunner between 10 and 11 February, he flew back and parachuted on 21 February. After being captured by the Red State Police, he died under observation in hospital, while awaiting prosecution on charges of treason.