Since the end of World War II, the United States has almost always viewed itself as a leader in resettling refugees forced to flee their homes around the world. But in just three years, President Trump has reduced the flow of refugees to a trickle.

Resettlement in the United States occurred through a series of ad hoc policies until 1980, when the Refugee Act, which passed with unanimous bipartisan support in the Senate and was signed into law by Jimmy Carter, established a bipartisan, internationally cooperative, public-private program housed at the State Department. The statute became the basis for the successful resettlement of more than three million refugees escaping violence and persecution.

The country can take pride in that sustained humanitarianism, which has also made the United States stronger.

But within a week of taking the oath of office, President Trump made it clear that his administration would be aggressively targeting refugee resettlement.

His first executive order, in January 2017, indefinitely suspended the resettlement of Syrian refugees, froze resettlement admissions and barred entry to citizens of seven Muslim-majority countries. Later that year, Mr. Trump announced that he was capping refugee admissions at 45,000, — less than half of the 110,000 the year before under President Barack Obama. It was the first time that the ceiling was below 67,000.

Refugees are the most thoroughly vetted group to enter the United States. In addition to a screening by the United Nations High Commissioner for refugees, the federal government conducts its own vetting process involving multiple law enforcement, national security and intelligence agencies, including fingerprint and biometric security checks, as well as medical screenings. The entire process can take more than two years.