900 (Motorized Demonstration Brigade) was formed 17 June 1941 by the German Army from school units in preparation for Operation Barbarossa.

[7] Lehr was still moving forward towards the demarcation line between German and Soviet-owned Poland on 22 June 1941 when Operation Barbarossa began and it missed the first few days of the campaign.

[8] By 19 July it was part of the northern wing encircling the Smolensk Pocket, but it quickly moved north-east to rebuff relief efforts by the Soviet 16th and 30th Armies of the Western Front.

[9] It was pulled off the front line into tactical reserve on 7 August 1941 and remained there for ten days until renewed Soviet attacks caused it to send it back into combat.

The Soviets forced the Germans to retreat from Kalinin after a month of heavy fighting and Lehr was placed in reserve on 12 November, where it remained until the Soviet Winter Counter-Offensive of 5 December forced the Germans to retreat en masse.