In the 1950s and 60s, the U.S. Army conducted training exercises using an imaginary enemy named, quite simply, Aggressor. The characteristics of Aggressor were worked out in realistic detail. Soldiers assigned to play the part of Aggressor troops had to learn the organization of its ranks and the types of weapons it used. They wore special uniforms and insignia and even carried fully realized fake identity papers. They also had to speak a different language, and that language, in a twist so ironic it is almost cruel, was Esperanto, the language of peace.
Esperanto was created in the 1880s by Ludwik Zamenhof, a sensitive soul who grew up in Eastern Europe among Yiddish, Russian, Polish, and German speakers who had nothing but hostility toward each other. As a child he felt "the heavy sadness of the diversity of languages," seeing it as "the primary force which divides the human family into enemy parts," and he vowed he would do something to solve this problem.
He created Esperanto, a hybrid of European languages with a simplified, regular grammar, designed to be easily learned. He hoped it would serve as a neutral linguistic common ground where people of different nations could meet without kicking up the dust of tricky history and power imbalance that their national languages couldn't seem to shake.
Surprisingly, after Zamenhof published a description of Esperanto in 1887, it really took off. The first international Esperanto congress was held in 1905, and over the next decade every year saw more Esperanto clubs, journals, magazines, and books. Membership in Esperanto organizations grew steadily.
At the same time, other inventors offered their own, competing versions of easy-to-learn European hybrid languages. They touted the superiority of their designs and advertised the practical advantages to commerce and science that their languages would bring, but none of those other projects lasted very long. People came to Esperanto for various reasons, but the ones who stayed and helped it grow were not in it for commerce or science or the particular qualities of the language. They were in it for the ideal: peace for humanity, brought about by a common language. They sang about it in their anthem, La Espero (The Hope):
En la mondon venis nova sento (Into the world came a new feeling)
tra la mondo iras forta voko (through the world goes a mighty call)
per flugiloj de facila vento (by means of the wings of a gentle wind)
nun de loko flugu ĝi al loko (now let it fly from place to place)
THE 'AGGRESSOR STOMP'
So how did Esperanto come to be, in the words of one Army field manual title, "the Aggressor Language"? Almost everything about it, except for the whole language-of-peace part, made it perfect for the Army's purposes. It had become, as stated in the field manual, "a living and current media of international oral and written communication" with a well-developed vocabulary. It was regular and easy to learn, at least to the level needed for drills, and most importantly, it was "consistent with the neutral or international identification implied by Aggressor." Using Spanish or Russian would have been politically problematic. Making up another language from scratch would have been too much trouble. Esperanto was neutral, easy, and there.
But what a century it had endured in order to be there! Esperanto's whole life was marked by war. Zamenhof's beloved brother killed himself when the Russians ordered him into the army during World War I because he couldn't bear the thought of once again experiencing what he had seen as an army doctor during the Russo-Japanese War. Zamenhof died soon after that, worn out from the news of destruction coming in from all corners of Europe. His children would survive, only to perish in the concentration camps of the next war. Esperantists were persecuted by Hitler, who saw the language as part of a Jewish conspiracy, and sent to the Gulag by Stalin, who saw it as a dangerous badge of cosmopolitanism.
Yet Esperanto survived, weakened, but with its peaceful ideals intact, despite the fact that the savage events of the intervening decades had rendered those ideals hopelessly naïve.
The field manual for the Aggressor language gives a brief description of Esperanto grammar which looks much like what is found in any Esperanto textbook, followed by a dictionary of useful terms which looks like the innocent dream of Zamenhof reflected in a distorted mirror of evil. Unlike most language learning dictionaries it does not include basic words like child (infano) or love (amo), but it does include the following:
armored carrier (kirasportilo), bombing run (bombardaproksimigo), tear gas (larma gaso), insubordination (malobeo), barbed wire (pikildrato), fire power (pafpovo), stab (pikegi), punch (pugnobati), lynch (linĉi), choke (sufoki), strafe (ŝtrafi), slash (tranĉo), poison (veneni), torture (torturi), kill (mortigi)
These are words you need when you're playing the enemy in a war game. It was a testament to the flexibility and productivity of Esperanto that the army was able to coin phrases, like senresalta pafilo (recoilless rifle) that had probably never been uttered by an Esperanto speaker before. It had also probably never occurred to an Esperantist that, as claimed in the 1960 Army Information Digest, "performing 'Aggressor Stomp' to orders barked out in Esperanto helps to instill in each man a feeling that the enemy he portrays is different from U.S. troops."
For the Esperantists, the language had always been a means to feel kinship in place of difference, and this ideal sometimes showed up in the unlikeliest places, displayed by real aggressors during real wars. After the occupation of the Netherlands in World War II, an Esperantist went to check on the building where the local club used to meet in Arnhem and found a note attached to the locked door. It had been left by a German soldier, and it said, in Esperanto, "the house is deserted. A visitor cannot go in. Will the 'mighty call' no longer 'go through the world'? Take courage, soon another time shall come! Long live Esperanto! –A German Esperantist."
The Army removed Esperanto from its field manual in the 1970s because it took too long to learn to be practical. Esperantists, unconcerned with mere practicality, continued speaking, joking, singing, fighting, and trying to bring people together in Esperanto. And they are still at it today.
In this U.S. Army informational film, you can see the Americans capture Aggressor prisoners and take them to a command post "where a U.S. interrogating officer was ready to go to work on them in their own language."