Mark Hetfield is the president and CEO of HIAS , the global Jewish nonprofit that protects refugees. The views expressed in this commentary are his own.

(CNN) President Donald Trump is commemorating International Holocaust Remembrance Day by slamming America's door on refugees. This is a ghastly repeat of the tragic mistake America made in 1921, when President Warren Harding signed the Emergency Quota Act, severely limiting the numbers of refugees and immigrants admitted to the country.

Even at the height of Holocaust, as millions of Jews, homosexuals, political dissidents and others were exterminated, the US kept its doors shut.

The Refugee Convention of 1951 arose from the ashes of the Holocaust to ensure that never again would the world turn refugees over to their executioners. How ironically tragic that Trump has chosen to observe Holocaust Remembrance Day by once again derailing America's commitment to refugee protection.

Trump's decision to pause an already secure program in the name of security is simply playing on public fear, vilifying refugees as dangerous just like America did in the 1930s and 1940s, when Jews from Germany and Austria were deemed as " security threats ."

Unfortunately, the stakes are even higher today. There are more refugees and displaced persons in the world now than there have been at any time since the Holocaust. Over 65 million people -- or one person in 113 -- have fled persecution in search of safety and freedom for themselves and their families.

Forgetting the lessons of the Holocaust, this executive order will have tragic results. We must remember that refugees are feeling terror, not bringing it. We must acknowledge that the world follows America's lead and that, if America does not stand up for refugees, very few other countries will.

The lesson here is that an international failure to welcome and protect refugees will lead to millions of vulnerable persons being trapped inside their countries of persecution, susceptible to being jailed, tortured or killed.

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History will look back on this executive order with shame. And Americans, who with a few notable exceptions, have been so welcoming of immigrants, will look back in horror. For most of American history, the United States has been a welcoming country, and refugees have made it that much stronger. Now, this basic tenet of integration is under fierce attack.

What makes this executive order even more tragic is how unnecessary is it. Today, with greater technological tools at our disposal than at any time in history, immigrants are subject to intense scrutiny: multiple interviews, fingerprints taken, computerized and kept, and repeated security checks by numerous security and law enforcement agencies.

In other words, refugees are already thoroughly vetted but, like so much else with Donald Trump, the facts do not seem to matter. He wants "extreme vetting."

Moreover, if America does not take refugees, who will? Last year, the United States only resettled 85,000 . Many other countries host far more refugees than we do.

However, it is the way we welcome refugees -- as new Americans -- that has always distinguished us. This is how America credibly demonstrates to the world that refugees should be protected and welcomed. Trump is depriving America of that credibility. If America is afraid of refugees, other countries will be too. If we stop accepting refugees, other countries will stop accepting them too.

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More than 1,500 rabbis from nearly every state in our great country chose this month, the month of international Holocaust remembrance, to join HIAS by signing a statement of welcome for refugees. In contrast, Trump observes Holocaust Remembrance Day by shutting America's door to refugees. This is, as they say in Yiddish, a shanda, or embarrassment.

It is appropriate at this time to adopt the words of the great Jewish sage Rabbi Hillel to the refugee situation and Donald Trump's "America First" slogan: "If America is not for itself, who will be for America? But if America is only for itself, what is America? And if not now, when?"

An America which turns away refugees is not America. We forgot that during the Holocaust. Let's never again forget who we are.