Progress was slowed by the overwhelming numbers of Germans to be processed, but also by difficulties such as incompatible power systems and power outages, with the Hollerith IBM data machine that held the American vetting list in Paris. As many as 40,000 forms could arrive in a single day to await processing. By December 1945, even though a full 500,000 forms had been processed, there remained a backlog of 4,000,000 forms from POWs and a potential case load of 7,000,000. The "Fragebögen" were, of course, filled out in German. The number of Americans working on denazification was inadequate to handle the workload, partly as a result of the demand in the US by families to have soldiers returned home. Replacements were mostly unskilled and poorly trained. In addition, there was too much work to be done to complete the process of denazification by 1947, the year American troops were expected to be completely withdrawn from Europe.