First Phase: The Tactical Breakthrough
Operation Bagration began on 22 June 1944, the same calendar day on which the Germans had previously invaded the Soviet Union in 1941, with probing attacks throughout the German lines. The main offensive began in the early morning of 23 June, with an artillery bombardment of unprecedented scale against the defensive works. Within hours, some sectors of the German defenses were in danger of being breached.
The first phase of Soviet deep operations, the "deep battle" envisaged breaking through the tactical zones and forward German defences. Once these tactical offensives had been successful, fresh operational reserves exploited the breakthrough and the operational depths of the enemy front using powerful mechanized and armoured formations to encircle enemy concentrations on an Army Group Scale.
Read more about this topic: Operation Bagration, The Battle