Certainly, as with all writing prompts, what you get here can be a guide for you to follow. Hopefully, enough in way of paths can be given to you so that you can generate an awesome speech.
I do believe that opening of your speech could be about how historical bias is present in many disciplines and fields of study. Students are regularly exposed to a gender bias in their studies of the past. It comes down to the committed historian and the critical thinker to be able to transcend the bias that exists in historical study and find the truth. It is in this light where one can discover the contributions of women in the field of espionage and intelligence operations. Being able to establish in your introduction how espionage and intelligence operations have been clouded by gender bias will create the atmosphere that your speech hopes to generate. It provides an introduction to how the topic area of your speech has been infected, to a certain extent, with bias. It is overcoming this intellectual condition that drives your speech.
In terms of the body of your speech, it is always effective to not overload your audience with so many examples. Three clear examples of women who have contributed much, but for whom there is little in way of recognition can help to illuminate how there has been misrepresentation in the historical narrative. The lack of voice is where misrepresentation lies. The efforts of Ruth Wilson is one such case study. In the midst of death and carnage that is the study of World War I, we fail to effectively understand the role of intelligence and espionage operations in the campaigns. The "modern war," World War I depended on nations being able to gather intelligence and engage in espionage operations. Your speech can discuss how the misrepresentation here is that we fail to actively acknowledge the contributions of women in this capacity. For example, students of World War I do not know the work of Ruth Wilson or Elizabeth Friedman, women who were responsible for advances in the field of cryptography and secret communications for the British side. They were codebreakers and pioneers both as women and as military operatives, as nations began to realize the strategic importance of breaking through enemy communique. In this regard, acknowledging the work of women like Wilson and Friedman do much to counteract the misrepresentation of women in the field of espionage history and military intelligence.
Another example of the misrepresentation of women in the history of espionage activities and military intelligence can be seen in the Cold War narrative. The traditional Cold War narrative is one in which the panache and strength of Ronald Reagan almost "willed" America into victory. That is an oversimplification. Essentially, American victory in the Cold War was predicated upon on the gathering of intelligence and using espionage to challenge Soviet authority. In this realm, women like Elizabeth Swantek, Juanita Moody, and Dorothy Blum were vital in obtaining intelligence through espionage operations. The fall of the Soviet Union can be attributed in large part to the role of women, historical giants who were airbrushed out of the historical narrative to glorify the role of male politicians. However, you can make the case that your speech is the first step in this process of setting the record straight, righting a wrong.
Since your speech is directed at the United Nations, you might want to make a case about how the reality of misrepresentation in espionage history and military intelligence might be rooted in a larger vision. The traditional picture of the agency of women in espionage history is set within a paradigm of sexism and silencing of voice:
A French perfume house, some years ago, launched a scent named "Clandestine," as in "clandestine woman." The advertising slogan assured prospective buyers that "there's something clandestine in every woman." The ad, then, drew on a specific cultural trope, that of an ineffable link between secrecy and femininity. This trope's most forceful image is, of course, that of the sexy woman spy, the ultimate embodiment of an underground feminine mystique. From Mata Hari onward, the spy/seductress, epitomizing as she does women's supposed "natural skills for duplicity," has become a cultural icon "that still informs our visions of gender, secrecy, and sexuality today," writes the historian Tammy Proctor in her fine study of women's intelligence work in World War One
Your speech can address how part of the challenge that is faced by women in espionage history and military intelligence is the stereotype of women as vixens. This oversexualized image of women silences voice and denies full humanity. No woman who served in the role of intelligence would ever believe that their job was the trope behind "Clandestine." Rather, it represented struggle, a fight to the death for a cause that was believed. In articulating how this image should be countered with a more authentic read of the history behind what it means to be a woman in the field of espionage and military intelligence, your speech can conclude with a rousing call to action. Perhaps, something like, "Act not as a blind soldier in the garrison of misrepresentation, but rather as a heroic figure in an army of transformation towards a more authentic view of women in intelligence and espionage history.