Your question is excellent and important, and I’m glad it has gotten popular because 1) there aren’t enough gender history questions around here and 2) it is a good example for the AskHistorian community to remember that there is tons of research left for historians to do, especially outside of Europe and the US. Your question is a social history question; but unfortunately, nearly everything written about the Paraguayan War is military and/or political history. To my knowledge, there has only been one article and one book chapter written about women in the Paraguayan War and its aftermath in English since the 1980s in English (“Following Their Children into Battle: Women at War in Paraguay, 1864-1870,” by Barbara Ganson in The Americas and “Protagonists, Victims, and Heroes: Paraguayan Women during the ‘Great War’” by Barbara Potthast, published in I Die With My Country). And if you know anything about the field of history in general, you’ll recognize that this is about the time that women’s history was invented. Two articles! There are probably a few I have missed, some in other languages, and a few passages or sections in books on the war itself, but still….just think about that for a second. That is about ALL scholars know about your question. Think about how much as been written about WWII. It is just stunning to me the difference. Basically for historians, this field of Latin American history is completely wide open for research. But it also means that any answer I provide is based on an absolutely miniscule number of peer-reviewed sources. AND on top of that, those articles are based on relatively accessible primary sources like newspapers, travel sources, and government documents (all of which can be problematic). To my knowledge, there is not the sustained, intense mining of archival material for every shrivel of detail about the life of women that has so revolutionized our understanding of women or gender in other parts of the world. My point is that there is really a ton that we don’t know very well on this question.

So first, people like to throw around shocking statistics about the War of the Triple Alliance, and they are right: the war was truly devastating. Unfortunately, population statistics from before and after the war are not well documented, so I do not feel comfortable saying definitively how many people died. There was a census in the 1840s and the 1870s. However, all of these censuses are imperfect, and (like four) historians who study this topic don’t agree on the numbers at all. One of the 1870s censuses seems to show that around 70% of the population of Paraguay vanished; one a few years later makes it seem like the number was 30ish% or that there was an absolutely massive spike in population (which is implausible given how devastated the country was). Women outnumber men in both censuses, but they also likely seriously undercounted. I just don’t trust the numbers. You can if you want. Others do. But I don’t. Regardless, the war (and mostly its resulting epidemics, starvation, chronic malnutrition, and displacement) devastated Paraguay. The survivors in Asunción describe the post-war city in apocalyptic terms. However, the 28,000 men statistic that you mention (if this is even close to accurate) is only of fighting-age men. This count does not include children, who probably made up a third to half of the population after the war. That meant that in post-war Paraguay, there was actually about a 3 to 1 female-to-male ratio, rather than a 10 to 1 ratio. Still remarkable. Still stunning. Still heartbreaking. But not so extreme.

Women played a massive role during the war. They ran the household and produced agricultural and homespun products necessary for familial survival and the war effort. They were ubiquitous in the Paraguayan armies’ camps, carrying out increasingly important support roles as the war dragged on. At first, they served mostly by caring for the wounded, cooking, and doing laundry, but later women ran the camps themselves, engaged in defensive constructions, and carried mail. The war forced thousands of families from their home as refugees, and Lopez evacuated towns and villages ahead of the advancing allied forces, which further dislocated the populations of Paraguay (feeding the spiral of malnutrition and disease). Families were also uprooted because many expressed dissatisfaction with the war, which resulted in the execution of men and women and also banishment.

Both of the articles mentioned above reach a surprising conclusion about the effects of the war on the place of post-war women: The war changed very little about their place in Paraguayan society. Women did not receive new political rights under the new constitution. In fact, despite their massive contributions to the war effort and efforts at familial survival, government and newspaper sources continued to emphasize the role of mother and worker devoid of any political opinion. Of course, we know that women did have political opinions and did protest through the courts, in newspapers, and in public to affect change, even though they weren’t supposed to.

In the immediate aftermath of the conflict, travel reports indicate that the population was starving, disease was widespread, prostitution was prolific, and sexual violence on women and girls was common. It was essentially a population of refugees in many parts of the country who had been unable to grow food for months or years. The Allied armies provided some food relief, and people streamed into the the capital. As life settled back down, women returned to the same work they did before the war, which included mainly household and agricultural work and as street vendors. The biggest change to women’s life after the war was that public education was opened to both males and females.

I hope someone will write a good social history of the war and its aftermath (or if one has been written, please let me know). We don’t know enough about how women navigated these times, let alone how women of African and indigenous descent experienced conflict. We don’t know enough about why women supported (or didn’t support) the war effort. We don’t know enough about sexual violence during or after the war. We don’t know enough about what women thought or how they saw themselves and their role in a post-war society. And I don’t think anyone has employed the theoretical concepts of women, gender, and sexuality studies to post-war Paraguay.

Follow up: did this asymmetry also result in detrimental decreases in biodiversity? That is, are Paraguayans disproportionately affected by genetically inheritable diseases relative to other countries?

/u/Bernardito has a great answer in Is there any information on dating in Paraguay after the Triple Alliance War? that goes into this a decent bit.

A short summary seems to indicate that there isn't a ton of documentation, and that immigration and returning soldiers filled some of the gap.

Followup: Did the war affect the other countries (Brazil, Uruguay, Argentina) similarly? If not, why was paraguay so affected?

There is this answer about Paraguyan demographics 8 months ago

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