Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The Czechoslovak government built a system of border fortifications from 1935 to 1938 as defensive countermeasure against the rising threat of Nazi Germany that later materialized in the German offensive plan called Fall Grün. The objective of the fortifications was to prevent the taking of key areas by an enemy (not only Germany, but also Hungary) by means of a sudden attack before the mobilization of Czechoslovak army could be completed, and to enable effective defense until the allies (France and possibly the Soviet Union) would help.