Lenski was born in the East Prussian village of Czymochen to a landowning family; his mother was a teacher of Masurian descent.

In 1912 Lenski joined the German Imperial Army and was promoted to a Fähnrich in the Grenadierregiment zu Pferde Nr.

[1] Lenski fought in World War I, initially as a platoon leader, and joined the staff of the Generalkommando z.b.V.

[1][2] In September 1942 Lenski took over the command of the 24 Panzer Division, which fought near Stalingrad, and was promoted to a lieutenant general on 1 January 1943.

After initial hesitation he joined the National Committee for a Free Germany and the Bund Deutscher Offiziere led by Walther von Seydlitz-Kurzbach on 7 May 1944.

Starting on 1 August 1952 he joined the staff of the East German paramilitary Kasernierte Volkspolizei (Barracked People's Police) and was responsible for the configuration of tank troops.