Wartime sexual violence
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. It symbolized revenge, subjugation and the enslavement of the defeated. Polybius describes Roman soldiers carrying out conquest rape, while Livy, portrays rape as synonymous with the capture of a city. Women and children were not the only victims of ancient wars.
Rape of adult men remains one of the most closely kept secrets possibly because it was incompatible with the notion of masculinity; being sexually submissive as a man was considered utterly unmanly, even for the ancient writers. In the Greco-Roman world a "true man" could play only an active role and those who were submissive were stigmatized. Tacitus mentions Roman recruiting officers dragging off the most striking Batavian boys to non-consensual sex (rape) saying it was one of the causes of the Revolt of the Batavi.
According to medieval historians, the Huns and Avars, who invaded Eastern Europe during Late Antiquity, harassed Wendish women and kept them in bondage as sex slaves:

Each year, the Huns [Avars] came to the Slavs, to spend the winter with them; then they took the wives and daughters of the Slavs and slept with them, and among the other mistreatments [already mentioned] the Slavs were also forced to pay levies to the Huns. But the sons of the Huns, who were [then] raised with the wives and daughters of these Wends [Slavs] could not finally endure this oppression anymore and refused obedience to the Huns and began, as already mentioned, a rebellion.
During Late Antiquity, India also saw countless invasions by warriors from Central Asia such as the Kushans, Hephthalites, and the Hunas. The Huna invasions of the Indian subcontinent helped hasten the decline of the Gupta Empire.
The Huna invaders conquered Kashmir, Punjab, and finally entered into the Ganges valley, in the very heart of India, slaughtering, pillaging, looting, burning, demolishing, and raping. Many cities in India were wiped out by the onslaught of the invaders; monasteries, temples, schools, and libraries were not spared, causing immense cultural destruction to the Indian subcontinent. Accounts are consistent that the Huna warriors practiced mass rapes of women in India.

Middle Ages: The Vikings were Scandinavians who raided and colonized wide areas of Europe from the late 8th century to the early 11th century. Viking settlements in Britain and Ireland are thought to have been primarily male enterprises, with a lesser role for female Vikings.  British Isles' women are mentioned in old texts on the founding of Iceland, indicating that the Viking explorers had acquired wives and concubines from Britain and Ireland. Some historians dispute the Vikings' "rape and pillage" image, arguing that exaggeration and distortion in later medieval texts created an image of treacherous and brutal Northmen.
Female slavery was common during the medieval Arab slave trade, where prisoners of war captured in battle as well as commercial slave trade from non-Arab lands sometimes ended up in sexual slavery as concubine slaves in the Arab world. Most of these slaves came from places such as Sub-Saharan Africa (mainly Zanj), the Caucasus (mainly Circassians), and Central Asia (mainly Tartars).
Before the Jurchens overthrew the Khitan, married Jurchen women and Jurchen girls were raped by Liao Khitan envoys as a custom which caused resentment by the Jurchens against the Khitan. Song princesses committed suicide to avoid rape or were killed for resisting rape by the Jin.
The Mongols, who established the Mongol Empire across much of Eurasia, caused much destruction during their invasions. Documents written during or after Genghis Khan's reign say that after a conquest, the Mongol soldiers looted, pillaged and raped. Some troops who submitted were incorporated into the Mongol system in order to expand their manpower. These techniques were sometimes used to spread terror and warning to others.
The Mongols invaded Hungary (Pannonia) and penetrated Austria almost to Vienna in 1241–1242. To the south of Vienna, they reached the Austrian town of Wiener Neustadt and devastated the countryside around the town, while they tortured and ate Austrian civilians indiscriminately regardless of their age, sex, fortune or class. The Mongol cannibal soldiers ate the deformed and old women right away, but they gang raped Austrian virgin girls and beautiful women to death before eating them and then cut their breasts off, reserving them for their leaders before eating the rest of their bodies according to Frenchman Ivo of Narbonne who was in the town itself before the Mongols eventually retreated to Hungary.
Images of Ivo of Narbonne's description of Mongol soldiers raping and eating European women appears in Chronica Majora by Matthew Paris.
Rogerius of Apulia's account of devastation and slaughter the Mongols wrought upon Europeans during the Mongol invasion of Hungary and Transylvania is in his book Carmen Miserabile.
During the 1241-2 Mongol invasion of Hungary, Mongol mass rapes of Hungarian women were recorded by the monk Rogerius who said they "found pleasure" in the act. The mass rapes of Hungarian women by the Mongols were recalled later when the Russian empire occupied Hungary in 1849 and when the Soviet army occupied Hungary in 1945.
In 1302, the army of Mamluk Sultan Al-Nasir Muhammad, who was of Kipchak Turkic descent, crushed a Bedouin rebellion in Upper Egypt and "slew mercilessly every Bedouin in the land and carried off their women captive". G. W. Murray said that "This drastic solution of the Bedouin question removed the pure Arab descendants of the Conquerors from the scene and so enabled the Beja to preserve themselves as an African race practically uninfluenced by Arab blood, while leaving the desert edges of Upper Egypt free for settlement by the Western Bedouin." The army was led by the Oirat Mongol Mamluk Sayf ad-Din Salar and Circassian Mamluk al-Baibars al-Jashnakir (Beibars).
During Timur's invasion of Syria, in the sack of Aleppo (1400), Ibn Taghribirdi wrote that Timur's Tatar soldiers committed mass rape on the native women of Aleppo, massacring their children and forcing the brothers and fathers of the women to watch the gang rapes which took place in the mosques. Ibn Taghribirdi said the Tatars killed all children while tying the women with ropes in Aleppo's Great mosque after the children and women tried to take refuge in the mosque. Tatar soldiers openly raped gentlewomen and virgins in public in both the small mosques and the Great Mosque. The brothers and fathers of the women were being tortured while forced to watch their female relatives get raped. The corpses in the streets and mosques resulted in stink permeating Aleppo. The women were kept naked while being gang raped repeatedly by different men. Ibn Arabshah witnessed the slaughters and rapes Timur's Tatar soldiers carried out. Mass rapes were also recorded in Timur's 1401 Sack of Damascus.

Early modern period: 

Ottoman conquests in Europe: In the Ottoman Empire, the practice of taking Slavic captives as slaves, including as sex slaves, was a notable aspect of the empire's expansionist and military activities, particularly in the Balkans and Eastern Europe. Slav populations, including those from regions such as the Balkans, Hungary, and Ukraine, were frequently targeted in Ottoman raids, known as "devshirme" or through warfare. Captured individuals were often enslaved and transported to various parts of the empire. Among these captives, young women and girls were particularly sought after for inclusion in the harems of the Ottoman elite. These harems were highly structured households that housed the women of the sultan and other high-ranking officials, where enslaved women were often used as concubines. They were sexually exploited including rape. Over time, some of these women, particularly those who bore children, could gain significant influence within the imperial court, although their initial capture and enslavement were marked by coercion and violence. The practice contributed to the demographic and cultural changes in the Ottoman empire, as many of these enslaved women converted to Islam and their offspring became integrated into Ottoman society.

Conquest of the Americas: Spanish conquistadors kidnapped and raped Native American women and children.

Sack of Rome: During the Sack of Rome in 1527, troops of the Holy Roman Emperor Charles V committed extensive sexual violence against the city's inhabitants.