VAN, Turkey — The German parliament’s vote Thursday to describe the mass killings of ethnic Armenians by Ottoman Turks a century ago as a genocide prompted an angry Turkish backlash and further strained relations between the two nations.

The motion passed with support from all parties in the Bundestag, meeting scant opposition in a nation that has long sought to come to terms with its own violent history and responsibility for the killings of six million Jews during the Holocaust.

The five-page motion, calling for “commemoration of the genocide of Armenian and other Christian minorities in the years 1915 and 1916,” drew swift fury from Ankara, which recalled its ambassador following the vote and vowed to take “necessary steps.”

“The way to close dark pages in [Germany’s] own history is not to defame the history of other countries with irresponsible and baseless parliament decisions,” Turkish Foreign Minister Mevlut Cavusoglu tweeted.

Politicians across the country expressed similar sentiments, with some labeling the decision null and void and an attempt to defame Turkey’s history, according to local media reports.

Turkish President Recep Tayyip Erdogan, who was visiting Kenya, reportedly said the decision “will seriously impact Turkish-German relations.”

German Chancellor, who officials said missed the vote for scheduling reasons, sought to calm Turkish outrage.

“Even if we have a difference of opinion on an individual matter, the breadth of our links, our friendship, our strategic ties, is great,” she said, according to reports.

The German government has traditionally been opposed to describing the killings as a genocide, for fear of upsetting Ankara, a major trade partner and member of the North Atlantic Treaty Organization.  German politicians are additionally wary of incurring a stinging political cost in a nation with some 3.5 million ethnic Turkish voters.

But German President Joachim Gauck, on the 100th anniversary of the killings last year, condemned the massacre as a genocide, prompting many members of parliament to brush aside the government’s resistance.

As Germany seeks to grapple with its past, recognition of the Armenian genocide has become a point of national reckoning. The resolution explicitly acknowledged Germany’s “inglorious” role for failing to halt a “crime against humanity” at the time of the killings.

Turkey has long challenged the use of the term “genocide” to describe the massacres beginning in 1915, arguing that the killings cannot be separated from the historical context of profound global upheaval around the time of World War I.

Historians largely agree that some 1.5 million Armenians were slaughtered in a state-organized campaign of ethnic cleansing and on long death marches into the Mesopotamian desert in what many consider the first genocide of the 20th century.

The killings – and widespread confiscation of Armenian lands – directly preceded the founding of the modern Turkish Republic, following the Ottoman collapse and Central Powers’ defeat.

Armenian President sent telegrams to Merkel and other officials thanking them for the decision and describing it as a “historic step,” the Associated Press reported.

“It’s a message to the entire world that crimes against humanity, even if they were committed more than a century ago, not only isn’t forgotten, but is justly condemned,” he said in the telegrams.

Shahan Jebejian, of Yerevan, Armenia, said his grandfather fled the forced marches into Mesopotamia and settled in the Syrian city of Aleppo as the only survivor from a family of 11.

“Everyone here in Yerevan is talking about it,” Jebejian said via Facebook.  “I tried to find other political reasons for recognition of the genocide. But I couldn’t. It was mostly genuine.”

Howard Eissenstat, a Turkey expert and historian at St. Lawrence University, said genocide denial has been incorporated into the Turkey’s “national memory, in which indigenous non-Muslims worked with Western powers to destroy the nation.”

“This narrative is absolutely central to the way Turkey has viewed its relations with the West and its own ethnic diversity,” he said.  “For most Turks, the resolution passed today is simply another example of this.”

Many Armenians, for whom recognition of the genocide forms a point of national catharsis, welcomed Germany’s decision.

“The expression of maturity by Germany with such a resolution is first of all a positive example that Turkey can use as a lesson,” said Harout Ekmanian, a lawyer and prominent commentator on Armenian issues based in New York.

The German decision comes at a time of acute global displacement. The EU is presently seeking continued Turkish support in stemming the flow of migrants and refugees to European shores.

Some analysts said that though the decision by Germany may upset Turkey, there probably will not be major political repercussions.

“In its current circumstances, diplomatically isolated and economically unstable, a significant fight with Germany would be extraordinarily costly” for Turkey, Eissenstat said