During the invasion of the Soviet Union in the early months of the war, rapid German advances almost captured the cities of Moscow and Leningrad. The bulk of Soviet industry which could not be evacuated was either destroyed or lost due to German occupation. Agricultural production was interrupted, with grain crops left standing in the fields. This caused hunger reminiscent of the early 1930s. In one of the greatest feats of war logistics, factories were evacuated on an enormous scale, with 1,523 factories dismantled and shipped eastwards along four principal routes to the Caucasus, Central Asia, the Ural, and Siberia. In general, the tools, dies and production technology were moved, along with the blueprints and their management, engineering staffs and skilled labor.