Editing Espionage (section)

=== World War I, World War II ===
In the 20th century, at the height of [[World War I]], all [[great power]]s except the [[United States]] had elaborate civilian espionage systems, and all national military establishments had intelligence units. In order to protect the country against foreign agents, the [[U.S. Congress]] passed the [[Espionage Act of 1917]]. [[Mata Hari]], who obtained information for Germany by seducing French officials, was the most noted espionage agent of World War I. Prior to [[World War II]], [[Nazi Germany|Germany]] and [[Empire of Japan|Imperial Japan]] established elaborate espionage nets. In 1942 the [[Office of Strategic Services]] was founded by Gen. [[William J. Donovan]]. However, the British system was the keystone of Allied intelligence. Numerous resistance groups such as the Austrian [[Heinrich Maier|Maier]]-Messner Group, the [[French Resistance]], the [[Witte Brigade]], [[Milorg]] and the Polish [[Home Army]] worked against Nazi Germany and provided the Allied secret services with information that was very important for the war effort.