context: The Smolensk battle, also the Smolensk strategic defensive operation is a complex of defensive and offensive operations of Soviet troops against the German Army Group Center and part of the forces of Army Group North in the main Moscow direction. For two months (from July 10 to September 10, 1941 year), fierce battles continued over a vast territory: 600-650 km along the front (from Idritsa and Velikiye Luki in the north to Loev and Novgorod-Seversky in the south ) and 200-250 km in depth (from Polotsk, Vitebsk and Zhlobin in the west to Andreapol, Yartsevo, Yelny and Trubchevsk in the east). At different times, they were attended by: from the Soviet side - ground forces and aircraft of four fronts (Western, Central, Reserve and Bryansk), as well as aircraft of the 3rd long-range bomber corps of the RGK; from German - troops of Army Group Center, part of the forces of Army Group North and aviation of the 2nd Air Fleet.
question: When did the Smolensk battle begin?
answers.text: July 10 to September 10, 1941