Lenski was born in the East Prussian village of Czymochen to a landowning family; his mother was a teacher of Masurian descent. Starting in 1903 he was educated at the Cadet School Köslin, Farther Pomerania and the Hauptkadettenanstalt Lichterfelde (Berlin) in 1908. In 1912 Lenski joined the German Imperial Army and was promoted to a Fähnrich in the Grenadierregiment zu Pferde Nr. 3 (Mounted Grenadier Regiment No. 3) in Bromberg on 22 March 1912.[1]