to determine the nature, location and scale of the Soviet buildup in the Soviet Far East. Based upon an initial underestimation of Soviet strength and on the monitoring of Soviet traffic on the Trans-Siberian railway, the Japanese believed that the Soviets would not have sufficient forces in place for an offensive before the end of August 1945, and that an attack was most likely in the autumn of 1945 or in the spring of 1946. Due to the withdrawal of the Kwantung Army's elite forces for redeployment into the Pacific Theater, the Japanese made new operational plans during the summer of 1945 for the defence of Manchuria against a seemingly inevitable Soviet attack. These called for redeploying the bulk of available forces from the border areas; the borders were to be held lightly and delaying actions were to be fought while the main force was to hold the southeastern corner in strength (so defending Korea from attack). Further, the Japanese had observed Soviet activity only on the Trans-Siberian railway and along the east Manchurian front, and accordingly prepared for an invasion from the east. They believed that when an attack occurred from the west, the redeployed forces would be able to deal with it. Although the Japanese redeployment in Manchukuo had begun, it was not due for completion until September 1945, and hence the Kwantung Army was in the midst of redeploying when the Soviets launched their attack simultaneously on all three fronts. Campaign The operation was carried out as a classic double pincer movement over an area the size of the entire Western European theatre of World War II. In the western pincer, the Red Army advanced over the deserts and mountains from Mongolia, far from their resupply railways. This confounded the Japanese military analysis of Soviet logistics, and the defenders were caught by surprise in unfortified positions. The Kwantung Army commanders were engaged in a planning exercise at the time of the invasion, and were away from their forces for the first eighteen hours of conflict. Japanese communication infrastructure was poor, and the Japanese lost communication with forward units very early on. However, the Kwantung Army had a formidable reputation as fierce and relentless fighters, and even though understrength and unprepared, put up strong resistance at the town of Hailar which tied down some of the Soviet forces. The Japanese defenders held out until 18 August, when 3,827