I'll start off by saying that this is a difficult question to answer. It is easiest to talk about the difficulties involved in answering the question, and then looking at the evidence that we do have which could inform a decision.

So, what evidence is there of sexual violence during the American Civil War? More than you might think, but also far far less than we would like. The most readily available source is American military court martial records. They contain somewhere in the range of 2-300 existing records for of rape or attempted rape perpetrated by Union army and navy personnel. State and county courthouses probably house many more such records from before 1863, likely squirreled away in some dank archive and simply have not been found yet. Prior to 1863 most crimes against persons were handled by whatever jurisdiction the crime took place in. Afterwards the General Orders No. 100, also called the Lieber Code, required that crimes committed by soldiers were to be handled by a military tribunal or court martial. The Lieber Code is super important piece of military code, and had lasting impact on how we conceptualize of war zones, military prisoners, occupied territory, and so on, but that is another tale.

Records of Confederate troops are even more rare. Confederate records on this kind of thing are basically non-existent because most of them were destroyed at the national level in the retreat from Richmond, or by state level records keepers in similar circumstances. At least we think they were, it is hard to prove when or why they were destroyed, but their absence is awfully conspicuous. When the war went bad for the Confederacy some feared being brought up on war crimes or charges of treason and attempted to destroy documentation that could connect them to what were illegal activities in the United States such as slave trading or managing prisons and so on. In the end many Confederate politicians and officers were given great leniency by the United States. The Confederacy also didn't keep great records in the first place, especially late in the war as they were basically bankrupt and they had more pressing matters. There was also infighting on who had authority to try troops by court martial anyway, as the individual states were loathe to allow other state legislatures or military tribunals have authority over their own state's soldiers, and as a result many crimes simply went untried. Confederate law also did not consider it a crime against a person to rape an enslaved person anyway, so it is doubtful that a court record would exist had it happened for the most commonly raped person in the Confederacy. The rape of a slave, after all, was considered a crime against property, and unless the enslaved person was injured in the commission of the rape their owner was unlikely to take someone to court over the matter.

There are also social considerations as to why we might have few records of rape. While we likely imagine the 1860s as a far more conservative time than it actually was, people still tended to be very private about personal matters. Appearing in the newspaper or being seen walking to court was still generally thought of as a bad thing and something which most people avoided. Women also had their so-called virtue to worry about maintaining, and if a rape was covered up they could keep their honor in the eyes of their peers. Keep in mind these are mostly middle and upper-class white concerns. Working class white people, enslaved people and free black people did not carry the same baggage around about honor and virtue and frequently engaged in legal disputes as it was often the only way to get restitution from someone with more power. I'm not really going to get into conceptions of virtue and honor here, but just keep it in mind as a mitigating factor. Then there are still the problems we have today regarding the underreporting of rape. Fear of revenge is a big one, as is the embarrassment and shame that can come with any sexual assault. Another common problem then and today is the rape of people engaging in sex work. If you think it is difficult to get a jury to side with you today on such an issue, 150 years ago it was all but impossible. To people of the 1860s someone engaging in sex work had basically thrown away their value anyway, so there was nothing left to take via rape. But attitudes were changing, and by the end of the war we start to see these people succeeding in some level in court cases. Black people also faced a tremendous uphill battle in even getting their case heard, even in the somewhat more tolerant North.

So we have some records, but what do they tell us about who are these soldiers committing their crimes against? Most people have an image in their mind of Union soldiers engaging in mass rape in Atlanta or Columbus, but this is most likely the products of Lost Cause authors pushing a narrative of Sherman as an invading Hun, or Grant as a drunk who can't control his men. Certainly soldiers did rape in those places, but they were not the carnivals of carnage of the popular imagination. We find little evidence that Sherman was any more cruel than any other commander North or South and certainly no evidence that he encouraged destruction beyond what he felt was militarily necessary. Most of the incidents of rape we know of are about what people expect to find anywhere else: a soldier, usually out alone in occupied territory decides to force himself upon a woman. Most typically an enslaved person or someone engaging in sex work part time or someone else equally vulnerable. They also happen as often in garrisoned towns against their "own people," and in a few cases we have soldier on soldier sexual violence. There doesn't seem to be much in the way of discrimination in who to they chose to rape, only an availability of suitably vulnerable targets. From young boys and girls, to the incredibly elderly and infirm, slaves to free people, the only thing that seemed to matter was availability to commit the crime with the smallest chance of getting caught.

The question that often comes up then is, was this more or less rape than we would expect to find in comparable wars? It is hard to say. First of all the American Civil War was a war without anything to compare itself to in American history. Historically civil wars tend to be particularly violent and destructive, but can also be places of incredible restraint. The Civil War is still responsible for more American deaths than every other American war combined, but also saw a surprising amount of civility between the opposing sides. Comparing the American Civil War to other wars like the American Revolution or the Napoleonic Wars, I tend believe there was less rape, but that almost comes down to a gut feeling. Francis Lieber, author of the previously mentioned Lieber codes fought for Prussia in the Napoleonic Wars and cited the incredibly cruel treatment of civilians and prisoners of war as one of the major factors in drafting up his code of behavior. He recounted robbing civilians of valuables and not just food, seeing starving prisoners cruelly treated, and plenty of murder whenever it was expedient. Even as recently as the American Revolution soldiers still occasionally engaged in the classicly imagined raiding of a town which often carried with it mass murder and rape. British troops raiding New Haven, Connecticut in 1779, in what is now called Tryon's raid carried out many terrible rapes either to spread terror or simply because they thought they had the right to do so. Later British besiegers of Badojaz, Spain, in 1813 reportedly engaged in a classical three day sacking spree. There are many records of this kind of behavior, it is not exclusive to British soldiers, they were just at my fingertips. This kind of behavior fortunately becomes rarer as we approach the Civil War. Either way this kind of comparison always makes me uncomfortable. It feels like saying Ted Bundy isn't as bad as Gary Ridgeway because he killed less people. At the end of the day people were raped, and any amount is too many.

So then you might ask, was the behavior of Civil War soldiers expected or was it out of the ordinary? That is also difficult to say. Standard of behavior varied from place to place and over time, but in general soldiers behaved as expected. To soldiers from Alabama raping a young black woman alone might not be unexpected, but to the men of a Massachusetts regiment it would be considered a terrible crime against a person. Generally soldiers marched where they were told, fought as expected, and refrained from breaking the law as they understood it. Attitudes about war were changing right as the American Civil War took place. Civilians were just starting to become civilians, a distinct group of people who deserved special protection from the carnage of war, and prisoners of war were believed to have some rights. Questions were being asked about what was acceptable behavior for soldiers with regards to enemy combatants and so on. By the end of the war the American public felt differently about the execution of war than they did at the beginning of the conflict. Such unprecedented levels of suffering should evoke great introspection and social change in a society.

The short of short answer is we don't really know how much rape occurred during the American Civil War, but there appears to be little reason to expect it to have been low as some authors have alleged. An absence of evidence is not evidence of an absence. And the often touted Victorian ideals of restraint, or a war of brother against brother get quickly cast aside in the realities of war. People were raped. Too many people by far, but what is most important is to see how America reacted to the unbridled carnage and suffering. Fortunately the American people did not seem to have the appetite for it, and conditions and behaviors improved greatly by the end of the war.