The U.S. House of Representative voted 393 to 0 Monday night that the Islamic State’s assaults on religious minorities in Iraq and Syria constitute genocide, a rare designation advocates hope will drive attention and action to the plight of the persecuted groups.

The measure was expected to pass, but even sponsors said they were surprised it was unanimous. Congress has only faced votes a few times on the complex legal and moral questions of whether heinous crimes qualify as genocide — and division is deep about what, if anything, the label mandates the U.S. government should do. One of the most hot-button topics as lawmakers considered this vote has been whether it could lead to the United States opening its doors to many thousands of refugees — Muslims, Christians and others. Immigration has been among the most explosive topics in the current presidential race.

The last time the House voted for such a resolution was in 2004, when it said genocide was being committed in Darfur. The Bush administration concluded that the designation — the White House also adopted it — did not mandate a change in its policy there.

Sponsors of Monday’s measure were overwhelmed by the vote, which is advisory and doesn’t mandate anything. However, it comes a few months after Congress passed a budget measure including a section calling for Secretary of State John Kerry to tell Congress whether the situation with Islamic State militants constitutes genocide — and included a deadline of  March 17 for him to do so. No vote is scheduled at the moment in the Senate.

The State Department declined to comment to The Post about its deliberations and whether it has a time frame for making a determination. However, in a briefing Monday, State Department spokesman John Kirby told reporters that the agency is continuing to review information and that Kerry has said he will come to a conclusion “soon.”

Asked if Kerry’s decision would be impacted by the House vote, Kirby said the former senator “understands the significance of that process. But I can tell you what he’s mostly focused on is making his determination based on evidence and analysis that he’s getting from the State Department. And I’ll also just say that he has taken very, very seriously and wants to make sure that whatever determination that he makes, it’s fact-based and that it’s adequately reflective of what we’re seeing on the ground.”

It’s unclear what evidence Kerry is reviewing. Various advocacy groups are highlighting different religious minorities, groups who live in various conflict areas with overlapping aggressors. Determining what happened and is happening is complex. The Holocaust Memorial Museum late last year put out a report saying its investigators had found evidence that Yazidis — an ancient faith made up of mostly ethnic Kurds — were victims of genocide, while the Catholic organization Knights of Columbus last week released a 280-page research document highlighting Christians as victims of ISIS genocide. Meanwhile, in the fall, dozens of members of the International Association of Genocide Scholars signed a document saying it believed ISIS has perpetrated genocide against “Chaldean, Assyrian, Melkite Greek and Coptic Christians; Yazidis, Shia Muslims, Sunni Kurds and other religious groups.”

In other words, this is complicated. However, several genocide experts say it’s unclear what legwork the Obama administration is doing on its own, if any.

“One thing that has troubled me is that I know of no organized government effort to investigate crimes committed,” said Cameron Hudson, director of the Holocaust Museum’s Center for the Prevention of Genocide. Hudson worked for the Bush White House in the mid-2000s and was involved in research then looking into the Darfur atrocities. A large team was sent to interview hundreds of people who fled violence and to take testimony, he said.

In the current case, “the U.S. government is using our report, eyewitness account from humanitarian groups and Christian groups. [In Bush’s Darfur probe] we were able to make independent determinations based on our own people. And I know of no similar [current] U.S. government effort to document crimes committed,” Hudson said. “The [Obama] administration has created a situation where they can be lobbied because they haven’t created research on their own.”

For many years, some Christians — particularly Catholics — have urged a focus on the deteriorating conditions for Christians in the Middle East, but the campaign has escalated significantly with the terrifying rise of Islamic State group, and has expanded to include more of the many religious minorities the militants terrorize.

“It is my sincere hope that this trans-partisan resolution will further compel the State Department to join the building international consensus in calling the horrific ISIS violence against Christians, Yezidis and others by its proper name: ‘genocide,’ ” said U.S. Rep. Jeff Fortenberry, a Nebraska Republican who introduced the measure.

Genocide is a specific legal term and scholars have disagreed over whether there has been sufficient evidence to call all religious minorities assaulted by Islamic State victims of “genocide,” rather than of war crimes or crimes against humanity, among other terms. There is also a web of varying lawmaker and advocate proposals about what the United States could do to help Islamic State victims that would be more successful than what the government is doing now. Monday’s House vote will certainly trigger debate, for example, about whether it means the United States needs to significantly open its borders to thousands of the Islamic State’s victims.

Greg Stanton, president of the group Genocide Watch, said he believes there would be an impact if the United States used the genocide designation to bring ISIS members to the International Criminal Court. “Let’s say ISIS wouldn’t be impressed. But it could galvanize the world. And I don’t mean just military action. I think we need a concerted effort to get Muslim countries especially to confront ISIS theologically and ideologically,” said Stanton, a former president of the International Association of Genocide Scholars. He is also advocating for the United States to give special refugee preference to groups found to be victims of genocide.

“What would have happened if we were not such an anti-Semitic nation during the Holocaust? We could have saved millions of people and we didn’t, we failed to do it,” Stanton said. “This is another case like that, where we could save literally thousands.”

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