A man exits the transit area after clearing immigration and customs on arrival at Dulles International Airport in Dulles, Va., last year. (James Lawler Duggan/Reuters)

When President Trump capped the number of refugee admissions at 45,000 over the fiscal year that began in October — just over half the number admitted in President Barack Obama's last full year in office — it was seen as a setback for hard-liners such as Stephen Miller, the White House's domestic policy chief, who wanted to set the limit drastically lower, possibly even at zero, and a victory for moderates in the Pentagon, State Department and elsewhere. That interpretation now looks flawed.

By means of an array of bureaucratic maneuvers, plus a security review of key countries ordered by Mr. Trump in late October, refugee admissions have plummeted to levels unseen in modern memory — and, for the first quarter of the current fiscal year, just a fifth the roughly 25,000 admitted in the same period a year earlier. At current trends, advocates say, the United States may grant entry to fewer than half the 45,000 refugees specified by Mr. Trump's limit; if so, it would be the lowest number since the current program was established in 1980.

That would render obsolete the assertion still in place on the website of the State Department's Bureau of Population, Refugees and Migration that boasts that America welcomes almost two-thirds of refugees settled in third countries, "more than all other resettlement countries combined." And it would be a milestone in the nation's ongoing retreat from its role as a great power prepared to grapple with the world's biggest flood of refugees since World War II.

The State Department cautions that the pace of refugee admissions may quicken this year. However, bureaucratic gears already set in motion are likely to stanch the flow of the world's most beleaguered people to U.S. shores for the foreseeable future.

A critical factor constricting admissions is Mr. Trump's 90-day review of refugees from 11 mainly Muslim countries, most in the Middle East and Africa, which together have generated more than 40 percent of all those admitted to the United States in each of the past three years, according to an analysis by Reuters. (Those same countries also account for roughly 60 percent of potential future refugees in the pipeline — those awaiting interviews with U.S. officials or various clearances for admission, according to refu­gee advocates.)

The review, though partially blocked by a federal judge last month, effectively choked off the refugee flow by also imposing burdensome new requirements to what was already an arduous security vetting process — even though refugees have been responsible for few terrorist attacks in the United States and Europe. A knock-on effect was that in response to uncertainty and State Department warnings about dwindling refugee admissions, independent contractors that run several hundred refugee resettlement offices nationwide are downsizing, thereby shrinking absorptive capacity.

At the same time, Homeland Security cut its deployment of interviewers who fan out through strife-ridden regions of the world to interview prospective refugees. In some cases, the admissions slowdown meant that one or another of a welter of required clearances from government agencies has expired for refugees awaiting final permission to enter the United States.

The administration's tactics amount to a stealth war on a program that has embodied America's compassion and global leadership. It is an attack on national identity of a piece with Mr. Trump's hostility to other forms of immigration and a symbol of the country's withdrawal from the world stage.