The recognition by some countries that there was a "genocide" of the Armenian people between 1915 and 1917 is furiously rejected by Turkey, although it does acknowledge people were massacred.
After the US House of Representatives passed a resolution Tuesday recognising the responsibility of the Ottoman Empire, Turkey's forerunner, here is some background.
- Genocide or massacre -
It is estimated that as many as 1.5 million Armenians were killed during World War I by troops of the Ottoman Empire, then allied with Germany and Austria-Hungary.
Turkey, which emerged from the dismantling of the empire in 1920, acknowledges 300,000 to 500,000 Armenians died during a civil war and famine.
But it denies there was any genocide, saying as many Turks were killed.
Clashes between Armenians and Turks had already started at the end of the 19th century, costing between 100,000 and 300,000 Armenian lives between 1895 and 1896, according to Armenian sources.
Turkey says the Armenians collaborated with the Russian enemy during World War I, and that tens of thousands of Turks were killed at their hands.
On April 24, 1915 thousands of Armenians suspected of being hostile to Ottoman rule were rounded up.
On May 26 a special law authorised deportations "for reasons of internal security".
The Armenian population of Anatolia and Cilicia was forced into exile in the Mesopotamian desert.
A large number were killed on the way or in detention camps. Many were burned alive, drowned, poisoned or fell victim to disease, according to foreign diplomats and intelligence services at the time.
Turkey's defeat in the war led to the creation of an independent Armenian state in 1918.
- Growing recognition -
Armenians have long sought international recognition of the events as genocide, which is defined in a 1948 UN convention as acts "committed with intent to destroy, in whole or part, a national, ethnical, racial or religious group".
In 1965 Uruguay became the first country to provide such recognition. France was the first major European country to use the disputed term in 2001.
In total parliaments in nearly 30 countries have passed laws, resolutions or motions recognising genocide. In some cases, however, only one chamber has passed a vote or it has been defined as non-binding, allowing the government to keep some distance.
The countries are: Argentina, Austria, Belgium, Bolivia, Brazil, Canada, Chile, Cyprus, France, Germany, Greece, Italy, Lebanon, Lithuania, Luxembourg, Paraguay, Poland, Portugal, Russia, Slovakia, Sweden, The Netherlands, Switzerland, United States, Uruguay, the Vatican and Venezuela.
Some countries even punish genocide denial, such as Cyprus, Slovakia and Switzerland.
However, the European Court of Human Rights ruled in 2015 that Switzerland's 2007 conviction of a Turkish politician for calling the genocide a "great international lie" was an infringement of the right to free speech.
On the 100th anniversary of the killings, Pope Francis in April 2015 described them as "the first genocide of the 20th century", becoming the first pontiff to publicly utter the term.
The European Parliament recognised the killings as genocide in 1987.
Germany's lower house did the same in 2016, although the German government said the vote was not legally binding.
Among the most recent recognition votes were in The Netherlands in 2018 and Portugal in 2019.
- United States -
The US vote Tuesday "affirming the United States record on the Armenian Genocide" was the most direct recognition of "the systematic murder of more than 1.5 million Armenian men, women and children by the Ottoman Empire."
The House had passed resolutions in 1975 and 1984 that referred to genocide but did not specify the responsibility of the Ottoman Empire.