The of the German–Soviet Nonaggression Pact signed on 23 August 1939, assigned the Republic of Estonia to the Soviet sphere of influence. On 24 September 1939, warships of the Soviet Navy appeared off Estonian ports and Soviet bombers began patrolling over the area around Tallinn. Moscow demanded that Estonia allow the USSR to establish Soviet military bases and station 25,000 troops on Estonian soil for the duration of the European war. The government of Estonia accepted the ultimatum, signing the corresponding mutual assistance agreement on 28 September 1939.