During the rapid German advances in the early months of the war, nearly reaching 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 harvests left standing in the fields that would later cause hunger reminiscent of the early 1930s. In one of the greatest feats of war logistics, factories were evacuated on an enormous scale, with 1523 factories dismantled and shipped eastwards along four principal routes to the Caucasus, Central Asian, Ural, and Siberian regions. In general, the tools, dies and production technology were moved, along with the blueprints and their management, engineering staffs and skilled labor.