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.

History of intelligence gathering: The Cold War

Read Next: History of intelligence gathering: The Cold War

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.

Another colorful and notable intelligence officer was Oskar Ritter von Niedermayer—a German general, professor, and adventurer. Sometimes referred to as the ‘German Lawrence’ (as in Lawrence of Arabia), Niedermayer is remembered for having led the 1915–1916 Persian and Indo-German-Turkish mission to Afghanistan and Persia during World War I in an effort to convince Emir Habibullah Khan to attack the British in India. This was a part of the Persian-Hindu-German conspiracy to boost the German war effort.

But no spy story is more controversial, murky, and tragic than that of the infamous Mata Hari. It is a story of how serious the business of intelligence operations are, and how quickly things can go from 007 to hell in a handbasket in no time at all.

Margaretha Geertruida “Margreet” Zelle MacLeod, better known by the stage name Mata Hari, a Frisian exotic dancer and courtesan who came from poverty, rose through the ranks of society by virtue of her beauty, cunning, and wit. Her looks, willingness to take chances (in this case, with her body), and ability to mesmerize crowds and individuals alike earned her fame and fortune…as well as the eye of certain intelligence services. As war moved across Europe and closed borders, MacLeod, by now known as Mata Hari, had greater freedom of movement as a citizen of neutral Holland and took full advantage of it. Before long, however, her travels and liaisons attracted the attention of both British and French intelligence services,who placed her under surveillance.

In 1916, Mata Hari fell in love with a 21-year-old Russian captain, Vladimir de Masloff, who was later sent to the front where an injury left him blind in one eye. She was determined to earn money to support him, and like countless agents before and after her, she accepted recruitment and an assignment to spy for France. Her handler was Georges Ladoux, an army captain who assessed that her courtesan contacts would be of use to French intelligence. Later insisting that her plan was to seduce her way into the German high command, Mata Hari met a German attaché and began tossing him bits of gossip, hoping to get some valuable information in return.

Instead, she intentionally or not ended up named as a German spy in communiqués sent to Berlin, which were promptly intercepted by the French. Here is where things began to get murky: Some historians believe that the Germans suspected Mata Hari was a French spy all along and set her up, deliberately sending a message falsely labeling her as a German spy—a message which they knew would be easily decoded by the French. Others, of course, believe that she was, in fact, a German double agent. Whatever the case, the French authorities arrested Mata Hari for espionage in Paris on February 13, 1917. She was later executed by firing squad.

Whether the truth behind her short-lived career as an intelligence agent will come to light or not remains to be seen. Some believe that Hari’s trial and execution were a distraction from Allied military failures. Mata Hari’s trial came at a time when the Allies were failing to beat back German advances, and real or imagined spies were convenient scapegoats for explaining military losses, with Mata Hari’s arrest one of many. Her supporters say that her handler, who turned against her at her trial, made sure that the evidence against her was constructed in the most damning way—by some accounts even tampering with it to implicate her more deeply.

In the end, the rapid onset of World War I forced most national intelligence services to modernize, revising tradecraft to fit the fluid political atmosphere, changing battlefield tactics, and embracing technological advances. The experience of the war formed the first modern intelligence services, serving as forbearers of the intelligence communities in France, Britain, Germany, and the United States today, but not right away. It seemed that, while those who have seen war will never forget, those who send others to war have tragically short memories. As the saying from George Santayana goes, “Those who cannot remember the past are condemned to repeat it.” Just over 20 years later, a lack of dedicated intelligence focus would see the same players once again march toward war.