After the June 18, 1914 assassination of Austria’s Archduke Ferdinand and his wife Sophie at the hand of a Serb nationalist, the coming conflict forced nations such as Germany, Russia, Britain, and France to honor treaties and mutual-protection agreements that had been made. By the time Austria-Hungary officially declared war on Serbia on July 28, 1914, a host of nations were already caught up in what came to be known as ‘The Great War’ and ‘The War To End All Wars.’ In the end, 16 million were dead and another 20 million were wounded. The years leading up to the outbreak of hostilities saw a decreased use of intelligence-gathering spies.

If the war officially began on July 28, then July 27 found most of the world’s nations with extremely weak or fledgling intelligence services—an issue that would become a pattern with many of the world’s so-called ‘superpowers’ between conflicts.

Russia operated a secret police and had agents of the czar for special internal circumstances, but its foreign intelligence capabilities were just about nonexistent. The French military and government both had trained intelligence services, but had no centralized agency to process and disseminate critical finished information. The United States had developed fairly robust domestic intelligence and investigative services in their naval and Army intelligence, and their Federal Bureau of Investigation.

Here is a bit of strange trivia: The Justice Department’s Bureau of Investigation (the forerunner of the FBI) was established in 1908 out of concern that Secret Service agents were spying on members of Congress. President Woodrow Wilson’s policy of open diplomacy made him suspicious of intelligence and gave him a general disdain for spies. It was not until the U.S. finally entered the war in 1917 that a serious devotion to fully developing foreign intelligence operations was taken on.

Britain had a well-developed military intelligence system, coordinated through the Office of Military Intelligence. British intelligence officers ran operations that covered the spectrum, from signals intelligence, or SIGINT (including wire taps), to HUMINT (human-based intelligence). The Brits had plenty of experience in foreign intelligence, with the vast expanse of British colonial holdings across the globe providing numerous outposts for intelligence operations. Britain was also among the first to employ agents devoted to the practice of industrial espionage, conducting wartime surveillance of German weapons manufacturing. In the eyes of many historians, it was Woodrow Wilson’s relationship with the British intelligence attaché in Washington D.C. that played a large part in the U.S. entering the war after resisting for so long.

Germany had apparently seen the writing on the wall, and had worked extensively to develop a sophisticated and far-reaching intelligence community. The civilian German intelligence service, the Abwehr, employed a comprehensive network of spies and informants across Europe, North Africa, the Middle East, and in the United States. German intelligence successfully employed wire taps, infiltrating many foreign government offices before the outbreak of the war. One early German victory came at the Battle of Tannenburg, when they used intercepted uncoded radio intelligence to ascertain that attacking Russian forces in the north and south were not coordinating, thus creating a weakness that German forces could exploit.

One of the most famous uses of intelligence during the war came as a result of British intelligence. When Germany began unrestricted submarine warfare against shipping in the Atlantic, her government assumed that the United States would enter the fight. Hoping to distract them from entering the war in Europe, Foreign Minister Arthur Zimmerman sent a coded message to the government of Mexico. In the message, Zimmerman proposed that Mexico attack the United States, and in return, Germany promised to reward them with territory that it had lost in the 1830s and 1840s, mainly Texas, New Mexico, and Arizona. The British were able to intercept, decipher, and deliver a warning to the United States government (here is where Wilson’s relationship with the top British spy in Washington comes into play). Six weeks later, the U.S. declared war on Germany.

The war had its share of notable (and infamous) intelligence officers and agents. On the German side, there was Walter von Gerich, a Finnish civil servant and later an agent in Germany during the war. In 1917, he was arrested while posing as German baron and diplomatic courier Walter von Rautenfels in Norway, and charged with planning sabotage. Gerich was caught with several suitcases filled with explosives marked as diplomatic luggage. Among the explosives were more than one hundred explosive bombs and one hundred firebombs, along with detonators and other supporting equipment. Citing his role as an official courier, diplomatic pressure from Germany convinced the Norwegians to release Gerich. Apparently not having the same immunity, several other involved persons were eventually sentenced to imprisonment.