 The Finnish strategy was dictated by geography. The frontier with the Soviet Union was more than 1,000 km (620 mi) long but was mostly impassable except along a handful of unpaved roads. In pre-war calculations, the Finnish General Staff, which had established its wartime headquarters at Mikkeli, estimated seven Soviet divisions on the Isthmus and no more than five along the whole border north of Lake Ladoga. In that case, the manpower ratio would favour the attacker by three to one. The true ratio was much higher; for example, 12 Soviet divisions were deployed to the north of Lake Ladoga.
