Leningrad Military District
In early 1939, the Leningrad Military District had already allocated 17 divisions, about 10% of the Soviet Army, to the Baltic states. Mobilizations followed shortly. The 8th Army was dispatched to Pskov on 14 September 1939, and the mobilized 7th Army placed under the Leningrad Military District. Invasion preparations were by now nearing completion. On 26 September the Leningrad Military District was ordered to "start concentrating troops on the Estonian-Latvian border and to finish that operation on 29 September." The order noted, "for the time of starting the attack a separate directive will be issued." On 24 September, warships of the Soviet Navy appeared off Estonian ports and Soviet bombers began threatening patrols over Tallinn and the nearby countryside. The USSR then entered the airspace of all three Baltic states, flying massive intelligence gathering operations on 25 September.