Despite the limitations on its size, their analysis of the loss of World War I, research and development, secret testing abroad (in co-operation with the Red Army) and planning for better times went on. In addition, although forbidden to have a General Staff, the army continued to conduct the typical functions of a general staff under the disguised name of Truppenamt (Troop Office). During this time, many of the future leaders of the Wehrmacht – such as Heinz Guderian – first formulated the ideas that they were to use so effectively a few years later.