The years between 1918 and 1939 were marked by intense turmoil for much of the world, as Europe, ravaged by World War I, struggled to rebuild and recover, while the U.S. brought home her late-to-the-war troops and once again downsized its military. In the Pacific, the Japanese military, who had played a limited role in the war on the side of the Entente, took advantage of Germany’s defeat to advance its interests in the region by acquiring the German military colony at Tsingtao, China. All of these events would form the perfect storm that would become the Second World War. The interwar years would find many of the world’s intelligence services lacking and playing catch up.


For Germany, the years between the world wars were as much a time of refitting and rearmament as they were of recovery. German territory had largely been untouched by the war, but being on the losing side came with consequences. An effective British blockade had brought about famine and hunger, and the largely unpopular war led to the Kaiser and the royal families abdicating, to be replaced by the Weimar Republic. Economically, Germany was suffering from hyperinflation at a time when the rest of the world was reeling from the effects of the Great Depression.

Abwehr, Germany’s military intelligence unit, was formally born in 1920. This was despite the provisions of the Treaty of Versailles, which clearly prohibited the formation of any German intelligence agency. Ignoring this, the German defense ministry established what they labeled as a “defense against foreign espionage.” (Over time, this would morph into something else completely.) The fledgling Abwehr was tasked with domestic and foreign intelligence gathering — the majority of it via HUMINT (human intelligence) — along with counterespionage.

Then in 1929, each individual military branch’s intelligence units were combined and placed under the umbrella of the Ministry of Defense under General Kurt Schleicher. Much like today, the Abwehr operated out of domestic and foreign stations. The foreign stations were first set up in neutral countries and then in occupied nations as the Blitzkrieg rolled on. In 1938, Hitler replaced the Abwehr with the OKW (or Oberkommando der Wehrmacht, “Supreme Command of the Armed Forces”) and made it a part of his personal sphere of influence.

German Admiral Wilhelm Canaris, the head of the Abwehr for most of the war (Wikimedia).

According to an article in the online publication The Armchair General, Germany’s greatest intelligence successes came via communications intercepts and deception. Allegedly, the famous German lieutenant general (later Field Marshal) Erwin Rommel gained his best intelligence from the American military attaché in Cairo. Rommel was able to read his dispatches and gain information on the disposition of British forces in North Africa.

German HUMINT officers operated throughout Europe, Russia (early on in the war and before), and even in Asia and the United States. They gathered intelligence and recruited spies to report on everything from enemy troop movements to their own neighbors.


Most historians view Japanese intelligence during the war as largely a failure. But not everyone agrees. In a 2009 book titled “Japanese Intelligence in World War 2,” Japanese scholar Ken Kotani cautioned that the naysayers are basing their opinion mostly on the latter years of the war when the Japanese Army and Navy were fighting enemies on multiple fronts. Kotani examined the pre-war and early war years. He argues that if it were not for the intelligence gathered by Japanese spies and communications intercept forces, numerous victories over Russia, China, and Great Britain would likely not have been possible.

HUMINT and SIGINT were the hallmark methods of Japanese spying against foreign targets, while the Kampeitai (IJA police) and the War Ministry’s Investigative Department handled counterintelligence operations. The Japanese also made extensive use of OSINT (open-source intelligence) collection and support from organizations such as the South Manchurian Railway Company and the Domei News Agency.