In the Prussian province of Posen, with a large Polish population, there was strong support for the French and angry demonstrations at news of Prussian-German victories—a clear manifestation of Polish nationalist feeling. Calls were also made for Polish recruits to desert from the Prussian Army—though these went mainly unheeded. An alarming report on the Posen situation, sent to Bismarck on 16 August 1870, led to the quartering of reserve troop contingents in the restive province. The Franco-Prussian War thus turned out to be a significant event also in German–Polish relations, marking the beginning of a prolonged period of repressive measures by the authorities and efforts at Germanisation.
On what date did Bismarkck receive the disturbing report on the Posen situation? (If the question is unanswerable, say "unanswerable")
16 August 1870