On Friday night, Donald Trump fulfilled one of his signature campaign promises: He issued an executive order banning Syrian refugees from entering the United States, indefinitely.

Fifth in a 10-part weekly series. The Politics of US looks at polarizing topics to help deepen understanding of the issues – and respect for those with differing views. This installment explores whether the US is striking the right balance between security and liberty in vetting Muslim refugees.

How the candidates in the 2016 presidential election fall on the issue.

The U.N.'s refugee agency reports that the number of displaced people is at its highest ever -- surpassing even post-World War II numbers, when the world was struggling to come to terms with the most devastating event in history.

The total at the end of 2015 reached 65.3 million -- or one out of every 113 people on Earth, according to the United Nations High Commissioner for Refugees (UNHCR). The number represents a 5.8 million increase on the year before.

Hungarians who voted Sunday overwhelmingly favored Prime Minister Viktor Orbán's policy to reject the EU plan to distribute refugees fairly across the bloc. Not enough voted to validate the result, but that may not indicate a public change of heart on immigration.

The administration admitted a total of 12,587 Syrian refugees during the just-ended fiscal year, exceeding the target President Obama declared last fall by 2,587 (20.5 percent).

Of the 12,587, the vast majority are Sunni Muslims – 12,363 (98.2 percent) – while another 103 are identified in State Department Refugee Processing Center data simply as Muslims and a further 20 as Shi’a Muslims.

The world is currently in the midst of the greatest refugee challenge in modern history. According to the U.N. High Commissioner for Refugees, or UNHCR, more than 65 million people were displaced across the globe as of the end of 2015—up from 59.5 million people a year earlier. Of those, more than 21 million are refugees, outside their home countries and in need of protection.

When Secretary of State John Kerry promised to respond more vigorously to the worldwide refugee crisis last year, more than 85 members of Congress signed onto a bill to shut down the entire refugee program. Texas Congressman Brian Babin, the bill’s sponsor, explained their view: “The most persecuted religious minority in the world have been Christians, and of these 70,000, soon to be 100,000 per year coming in from the Middle East, less than four percent are Christian.”

Over the past five years, more than 9 million Syrians have fled for their lives. Three million have sought refuge in neighboring countries, and 6.5 million are internally displaced. According to the U.N. High Commissioner for Refugees, or UNHCR, more than 1 million refugees traveled to Europe by sea in 2015, and more than 80,000 refugees arrived there in the first six weeks of 2016 alone.

Does resettling Syrian refugees in the United States pose a threat to American national security? The question has dogged public debate in recent weeks. Prominent politicians have called the refugees “a Trojan horse” and suggested that only Christians be admitted, prompting outrage from Muslim-American advocacy groups and beyond.