On 20 July, the producers went on another expedition, to Dorogobuzh, in order to film the Battle of Borodino and the related parts of the plot. Photography could not be carried out in Borodino itself, mainly because of the many memorials located there. On 1 August, work was commenced. The shooting of the battle itself began on 25 August 1963 – its 151st anniversary by the Julian Calendar. 13,500 soldiers and 1,500 horsemen substituted for the historical armies (Several reports in the Western press have put the number of soldiers who participated at 120,000; however, in an 1986 interview to "National Geographic", Bondarchuk stated: "That is exaggeration, all I had was 12,000.") The troops were supposed to return to their bases after thirteen days, but eventually remained for three months. 23 tons of gunpowder, handled by 120 sappers, and 40,000 liters of kerosene were used for the pyrotechnics, as well as 10,000 smoke grenades. Tens of thousands of cubic meters of soil were dug out to construct earthworks resembling the Bagration flèches and the Raevsky redoubt. The set was divided to sectors, and a system of loudspeakers was installed – one for each area – to enable the director to coordinate the troops' movements. On 4 November, the session ended and Bondarchuk went back to Moscow.