Wartime sexual violence
In September 1999, the United Nations published a "Report of the International Criminal Tribunal for the Prosecution of Persons Responsible for Genocide and Other Serious Violations of International Humanitarian Law Committed in the Territory of Rwanda and Rwandan Citizens Responsible for Genocide and Other Such Violations Committed in the Territory of Neighboring States between 1 January and 31 December 1994". The report states that on 2 September 1998, Trial Chamber I of the International Criminal Tribunal for Rwanda, composed of Judges Laïty Kama, Presiding, Lennart Aspegren and Navanethem Pillay, found Jean Paul Akayesu guilty of 9 of the 15 counts proffered against him, including genocide, direct and public incitement to commit genocide and crimes against humanity, murder, torture, rape, and other inhumane acts. The Tribunal found Jean Paul Akayesu not guilty of the six remaining counts, including the count of complicity in genocide and the counts relating to violations of Common Article 3 to the Geneva Conventions and of Additional Protocol II thereto. On 2 October 1998, Jean Paul Akayesu was sentenced to life imprisonment for each of the nine counts, the sentences to run concurrently. Both Jean Paul Akayesu and the Prosecutor have appealed against the judgement rendered by the Trial Chamber.

International Criminal Tribunal for the Former Yugoslavia: Rape first became recognized as a crime against humanity when the International Criminal Tribunal for the former Yugoslavia issued arrest warrants in 1993, based on the Geneva Conventions and Violations of the Laws or Customs of War. Specifically, it was recognized that Muslim women in Foča (southeastern Bosnia and Herzegovina) were subjected to systematic and widespread gang rape, torture and sexual enslavement by Bosnian Serb soldiers, policemen, and members of paramilitary groups after the takeover of the city (April 1992). The indictment was of major legal significance and was the first time that sexual assaults were investigated for the purpose of prosecution under the rubric of torture and enslavement as a crime against humanity. The indictment was confirmed by a 2001 verdict by the International Criminal Tribunal for the former Yugoslavia that rape and sexual enslavement are crimes against humanity. This ruling challenged the widespread acceptance of rape and sexual enslavement of women as intrinsic part of war. The International Criminal Tribunal for the former Yugoslavia found three Bosnian Serb men guilty of rape of Bosniak (Bosnian Muslim) women and girls (some as young as 12 and 15 years of age), in Foča, eastern Bosnia-Herzegovina. Furthermore, two of the men were found guilty of the crime against humanity of sexual enslavement for holding women and girls captive in a number of de facto detention centres. Many of the women subsequently disappeared. However, Justice Richard Goldstone, chief prosecutor at the International Criminal Tribunal for the former Yugoslavia, commented that "rape has never been the concern of the international community."

United States: United States law specifies that rape in wartime is punishable by death or imprisonment under Section d(g) of the War Crimes Act of 1996. However, a total ban on abortion is a requirement of US humanitarian aid for war victims, with no exceptions for rape, incest, or to save the life of the mother.

Rome Statute: The 1998 Rome Statute Explanatory Memorandum, which defines the jurisdiction of the International Criminal Court, recognizes rape, sexual slavery, enforced prostitution, forced pregnancy, enforced sterilization, "or any other form of sexual violence of comparable gravity" as crime against humanity if the action is part of a widespread or systematic practice.

21st century: In 2008, the U.N. Security Council adopted resolution 1820, which noted that "rape and other forms of sexual violence can constitute war crimes, crimes against humanity or a constitutive act with respect to genocide".
The Office of the Special Representative of the Secretary-General on Sexual Violence in Conflict (SRSG-SVC) was established by Security Council Resolution 1888 (2009), one in a series of resolutions which recognized the detrimental impact that sexual violence in conflict has on communities, and acknowledged that this crime undermines efforts at peace and security and rebuilding once a conflict has ended. The office serves as the United Nations' spokesperson and political advocate on conflict-related sexual violence, and is the chair of the network UN Action against Sexual Violence in Conflict.
In April 2010, the first Special Representative, Margot Wallström of Sweden, established the Office and served as the United Nations' spokesperson and political advocate on this issue. In September 2012, Zainab Hawa Bangura of Sierra Leone took over as the Special Representative of the Secretary-General on Sexual Violence in Conflict.
The six priorities of the office are:

to end impunity for sexual violence in conflict by assisting national authorities to strengthen criminal accountability, responsiveness to survivors and judicial capacity;
the protection and empowerment of civilians who face sexual violence in conflict, in particular, women and girls who are targeted disproportionately by this crime;
to mobilize political ownership by fostering government engagement in developing and implementing strategies to combat sexual violence;
to increase recognition of rape as a tactic and consequence of war through awareness-raising activities at the international and country levels;
to harmonise the UN's response by leading UN Action Against Sexual Violence in Conflict, a network of focal points from 13 UN agencies that amplify programming and advocacy on this issue in the wider UN agenda;
to emphasize greater national ownership.
The Office has eight priority countries: Bosnia and Herzegovina; Central African Republic (CAR); Colombia; Côte d'Ivoire; Democratic Republic of Congo (DRC); Liberia; South Sudan and Sudan. While six of the eight priority countries are in Africa, this problem is widespread and the Office of the Special Representative is engaged on this issue in Asia and the Pacific (in Cambodia for residual cases from the Khmer Rouge period) and the Middle East (Syria).

2010s-today: In 2013, the U.N. Security Council unanimously passed Resolution 2122, which supported abortion rights for girls and women raped in wars, "noting the need for access to the full range of sexual and reproductive health services, including regarding pregnancies resulting from rape, without discrimination." United Nations Secretary General Ban Ki-moon had recommended to the U.N. Security Council earlier in 2013 (in September) that girls and women raped in war should have access to "services for safe termination of pregnancies resulting from rape, without discrimination and in accordance with international human rights and humanitarian law." In March 2013, Ban Ki-moon had also recommended to the Council that women raped in war have access to abortion services.
Sexual violence against women in 21st-century warfare remains a major issue in various conflicts worldwide, including but not limited to the Syrian Civil War, conflicts in the Democratic Republic of Congo, and the ongoing conflict in Yemen; women continue to be subjected to rape, sexual slavery, and other forms of gender-based violence.
In the Yazidi genocide, ISIS perpetrated widespread violence against women, subjecting them to systemic sexual slavery, rape, and brutal forms of abuse, underscoring the heinous nature of their crimes against the Yazidi community.
In Hamas' surprise attack on Israel in 2023, Hamas performed acts of sexual violence against Israeli women, including mutilation, rape and torture. According to an investigation of New York Times journalists, who used video footage, photographs, GPS data from mobile phones and interviews with more than 150 people, there were at least seven locations where sexual assaults and mutilations of Israeli women and girls were carried out. They concluded that these were not isolated events but part of a broader pattern in which Hamas "weaponized sexual violence" during the attacks.
In the Israeli invasion of Gaza, a report published in February 2024 by the United Nations Office of the High Commissioner for Human Rights found credible evidence of "egregious human rights violations" perpetrated by the Israeli Defense Forces against Palestinian women and girls. The experts were "shocked by reports of ... deliberate targeting and extrajudicial killing” of Palestinian women and girls in Gaza.  The report condemned the “arbitrary detention” of women and children who were subjected to “inhuman and degrading treatment,” including rape, strip searches, threats of sexual violence, and other forms of sexual and psychological abuse such as withholding of food and medical treatment.

History: 

Antiquity: Rape has accompanied warfare in virtually every known historical era. Women's historian Gerda Lerner writes,

The practice of raping the women of a conquered group has remained a feature of warfare and conquest from the second millennium B.C. to the present. It is a social practice which, like the torture of prisoners, has been resistant to "progress", to humanitarian reforms, and to sophisticated moral and ethical considerations. I suggest this is the case because it is a practice built into and essential to the structure of patriarchal institutions and inseparable from them. It is at the beginning of the system, prior to class formation, that we can see this in its purest essence.
The Greek and Roman armies reportedly engaged in war rape, which is documented by ancient authors such as Homer, Herodotus, Livy and Tacitus. Ancient sources held multiple, often contradictory attitudes to sexual violence in warfare. Haaretz writer and archaeologist Terry Madenholm explains that rape did not only serve as an instrument of sexual gratification or a tool for anger relief management.
For the Roman army, rape was more than just a weapon of terror; rape was regarded as the right of the victorious.