Armenia’s occupation of the territories of Azerbaijan was accompanied by atrocities that led to the ethnic cleansing of the indigenous civilian population of those territories. This was carried out in such a consistent and systematic way that clearly indicated it was planned, ordered and implemented by Armenia’s government.
Armenia’s armed forces followed the same military tactics while occupying cities, towns, settlements and villages of Azerbaijan: militarily encircling residential areas where possible; indiscriminate fire targeting civilians to kill as many as possible; taking hostages with mass rapes, tortures and other degrading treatment.
As a result of Armenia’s occupation of the territories of Azerbaijan in early 1990s, 20 000 people were killed, 50,000 people were wounded or became disabled, about 4,000 citizens of Azerbaijan are still missing. All captured areas were ethnically cleansed of more than 700,000 Azerbaijanis. Likewise, about 250,000 Azerbaijanis were expelled from Armenia at the end of 1980s. Thus, the Azerbaijani population once comprising majority in the territory of the present day Armenia were completely ethnically cleansed from their ancestral lands.
The Parliamentary Assembly of the Council of Europe confirmed in its resolution 1416 (2015) that [Armenia’s] military operations “led to large-scale ethnic expulsion and the creation of mono-ethnic areas which resemble the terrible concept of ethnic cleansing.”
Former President of Armenia Serj Sargsyan who used to be in charge of the military operations during the occupation of the territories of Azerbaijan confessed in one of the interviews he gave to a foreign journalist that “our war somehow differed from others. We had it so that ethnic cleansing took place. Otherwise was not possible.” In the same interview, Serj Sargsyan stated in the context of the massacre in the town of Khojaly that “if civilian population stays there … then it means that it also participates in the military actions.” 
This is a clear statement that Armenia’s armed forces regarded the civilian population of the occupied territories as military targets. By doing so, Armenia grossly violated International Humanitarian Law and disregarded its most important principles, namely that of the principle of distinction between civilians and combatants and the principle of military necessity. This state bears responsibility for war crimes, crimes against humanity and acts of genocide committed in the course of war it unleashed against Azerbaijan.
Atrocities against the civilian population and ensuing ethnic cleansing committed in the occupied territories of Azerbaijan are not an isolated case. Historically, atrocities and ethnic cleansing by Armenia’s forces have been committed in several Azerbaijani-populated areas, including in Zangezur. In 1918-1920, Armenia’s forces committed atrocities and ethnically cleansed more than 200 villages in the Zangezur uezd (currently Syunik region of Armenia). Armenian historian Razmik Panossian refers to the Zangezur events as “ethnic cleansing” that “enhanced the country’s [Armenia’s] demographic balance in favour of the Armenians.”
 Resolution 1416 (2005) of Parliamentary Assembly of the Council of Europe https://assembly.coe.int/nw/xml/XRef/Xref-XML2HTML-en.asp?fileid=17289&lang=en
 Transcript of interview by Thomas de Waal with Serzh Sarkisian, then minister of defense of Armenia (former president of Armenia), 15 December 2000, 2012, Carnegie Endowment For International Peace. http://carnegieendowment.org/files/DeVaalinterview_r.pdf
 For more information about Armenia’s crimes, please visit the relevant sections of the web-page
 Panossian, Razmik, The Armenians. London: C. Hurst & Co., 2006, p.255