A Marine strings concertina wire on the southern border. (U.S. Marine Corps)

The U.S. soldier was ready to deploy across the world at a moment’s notice, but when the orders came down weeks ago to mobilize on the southern border, it sparked a flash of concern.

He knew the mission was in support of border agents combing harsh borderland terrain to arrest anyone unlawfully in the country.

People like him.

“I’m an illegal immigrant,” the Chinese-born soldier told The Washington Post by phone.

His duties do not often intersect with Customs and Border Protection agents, he said, but he has avoided them out of fear they will learn that one of 5,400 troops in their orbit is in violation of immigration law.

That has placed him in the unusual situation of serving a nation that has not recognized him as a citizen, despite promises from the Pentagon to quickly naturalize skilled immigrants in exchange for service, as they had done for thousands of troops since 2009.

The Post is withholding the soldier’s name and certain details, including his duty location, because he fears discipline for speaking to the media.

The soldier, now in his late 20s, began his path to the United States nearly a decade ago, after high school.

His home in southeastern China is beautiful, he said, the region dotted with lakes and towering limestone karst formations. But it is also stifling. He felt trapped by family expectations, and a passion for engineering could take him only so far there.

There were better opportunities in America, he believed.

He joined his sister in California on a student visa and enrolled in college. The military seemed like a place to further his career, he said, and the Pentagon’s immigrant recruit program guaranteed something more than job security: “A sense of pride,” he said.

His enlistment would also harness something that makes him especially valuable to the military — his voice. He speaks Mandarin Chinese, which is among several languages the Pentagon has deemed strategically vital but in short supply among U.S.-born troops.

And as the Pentagon has increasingly worried about China’s military ambitions, it seemed like the perfect time, then, for the Chinese-born soldier to offer his skills. He was scheduled to begin training in August 2016, according to documents obtained by The Post.

That’s about when everything started to go very wrong. The Pentagon program he enlisted through, Military Accessions Vital to the National Interest, was beginning its year-long implosion.

Immigrant recruits commonly timed their enlistment so their student and visitor visas could carry them through with enough time to legally protect them. The Chinese soldier enlisted when he was still a lawful immigrant with a valid visa — in compliance with MAVNI requirements.

But the Pentagon’s security screening was so slow that “some number of 4,300 MAVNI applicants” had fallen out of lawful status as they waited, according to an internal agency memo dated Sept. 30, 2016.

The agency later said the number crested at 1,000 recruits. That number included the Chinese soldier, whose enlistment date slid back amid the chaos. Many recruits waited months, or years, to move forward.

The Chinese soldier did not even have weeks. In September 2016, the Pentagon introduced vastly more complicated security checks amid fears of foreign infiltrators.

Weeks later, in October, his legal status expired, making him an unlawful immigrant.

He picked up fares as a Lyft driver while he waited for his enlistment to move forward, he said, and took pains to avoid the border when he ventured to San Diego. He wouldn’t risk flying, either.

In August 2017, after nine grueling months under threat of deportation, he was granted deferred action by Citizenship and Immigration Services (USCIS), but that already expired, he said, putting him back into the crosshairs of immigration enforcement.

The MAVNI program was shuttered last fall, crushed by its own bureaucratic inertia, and remaining applicants in the system trickled through enlistment.

Military naturalizations plummeted just as the Chinese soldier readied for training, and USCIS closed its offices at three basic training sites in January 2018, BuzzFeed reported.

The agency said it did so after rule changes mandated 180 days of service to naturalize. In response, it moved to a roving model to perform naturalization services, though it did not say how troops like the Chinese soldier could fall through the cracks.

Congress mandated faster naturalizations established after a U.S. soldier from Trinidad was killed in Iraq on his way to gather paperwork for his citizenship. A Pentagon spokeswoman did not return a request for comment on how and why immigrant troops may arrive at their units without being naturalized.

Soon after the January closures, the Chinese soldier made it to basic training.

His drill sergeants told him he would not be naturalized during basic training in Missouri, he said.

He then moved to advanced training in Texas. He said he was told the base was not set up for naturalizations, either.

And then, soon after he arrived at his home station, he was mobilized for the border deployment.

In China, his parents have worried about his status and his safety after seeing images of Central American migrants fleeing tear gas. He feels sympathetic to fellow immigrants, he said, who like him left their home to pursue opportunities elsewhere.

“At the same time,” he said, “a massive group rushing in wasn’t the best way to do so, I think.”

At his new unit, he said paperwork for his naturalization was underway but that the border deployment has paused the process while he is gone.

Troops on the border were scheduled to leave by Dec. 15. But on Tuesday, the Pentagon extended forces there to the end of January, leaving him more time to ponder the risks of interacting with federal agents there.

He has kept busy in his down time by working out, reading and studying for certification tests on his smartphone, he said.

Sometimes he will catch a sunset of brilliant orange and pink.

It’s wondrous out there, he said, in the big, beautiful country not quite his home.

This story has been updated.

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