Every year, when the factory closed for the Diwali holidays, Amrit would come back to visit. The friends would walk about the village, Saiyub told me. He was working construction at the time, whenever there was an opportunity. Amrit spoke about the factory, urging his friend to move to the city. “I will find you a job in Surat,” Amrit promised.

Precise numbers are hard to arrive at, but scholars of urbanization and migration estimate that India has more than a 100 million migrant workers. The majority come from the impoverished northern Indian states which, like the American Rust Belt, have suffered decades of decline. They find work in the manufacturing and services powerhouses in western India, the national capital region of Delhi and increasingly the fast-growing states in southern India.

“Way back from the 1960s Indian government policies encouraged industry in the western and southern areas — India’s major capitalists came from those regions and preferred investing there,” said Rathin Roy, one of India’s leading economists. “Most politicians in the north were rural folk who saw the few pockets of industry as sites for rent-seeking.”

For Saiyub, migrating to a city wasn’t much of a choice. In the winter of 2015, he left the village with Amrit. After a 36-hour train journey from the nearby town of Basti, they arrived in Surat. They rented a room together for 2,000 rupees, or about $27, a month near Amrit’s factory. A few days later, Saiyub got a job, with Amrit’s help, at a factory that produced thread.

Saiyub started his work at 7 a.m., stopped for a lunch break and continued till 7 p.m. “We would go home for an hour, eat dinner and return at 8 p.m.” He worked another four hours till midnight, returning to his room to sleep for six hours, before setting out for the factory again. I was struck by the 16 hour shifts, but he brushed that off. “We could stop for a bit. It is not that bad.”

On his arrival in Surat, Saiyub had some apprehensions about being Muslim and working in Gujarat, Mr. Modi’s home state and the strongest bastion of Hindu nationalism. Throughout the five years he spent there, he read the news of attacks on Muslims in India but avoided speaking about politics in the factory. “Nobody bothered me,” he said. “I did my job. I got paid.”