After Germany invaded the Soviet Union on 22 June 1941, the Wehrmacht crossed the Estonian southern border on 7 July. The Red Army retreated behind the Pärnu River – Emajõgi line on 12 July. At the end of July the Germans resumed their advance in Estonia working in tandem with the Estonian Forest Brothers. Both German troops and Estonian partisans took Narva on 17 August and the Estonian capital Tallinn on 28 August. After the Soviets were driven out from Estonia, German troops disarmed all the partisan groups.

Answer this question, if possible (if impossible, reply "unanswerable"): When did the Red Army fall back to the Parnu River?
12 July