For most of its existence, Huawei was opaque to people in China, too.

It was founded in 1987, but it did not begin publishing the names and biographies of its board members until its 2010 annual report. Mr. Ren spoke to the news media for the first time in 2013. The next year, he told The Independent of London that he had no hobbies, prompting a colleague to lean in and suggest that he enjoyed reading and drinking tea.

Mr. Ren was born in 1944, in the mountainous southwestern province of Guizhou. His parents were teachers; he was one of seven children. His father, Ren Moxun, was the son of a master ham maker in Zhejiang Province. When he was growing up, Mr. Ren wrote in a 2001 article, the family was so poor that he did not own a proper shirt until after high school.

According to an official company biography, he studied engineering in college and joined the Chinese military’s infrastructure engineering corps in 1974 to help build and run a factory manufacturing synthetic fibers for textiles. At a time when China had no private-sector economy to speak of, it was not unusual for college graduates to join the military.

The infrastructure engineering corps was disbanded in 1983, according to the official biography. A few years later, Mr. Ren and business partners founded Huawei in what he called, in a 2016 interview with the official news agency Xinhua, a “run-down shack.” The company started as a reseller of telephone equipment imported from Hong Kong, but later started developing its own technology.

As it expanded around China and then across the world, Huawei inculcated a die-hard competitive spirit in its employees, pushing them to work harder and move faster than the company’s rivals. Huawei still speaks proudly of its “wolf culture.”

“We will always have wolf culture,” Mr. Ren said in an interview last year with Xinhua. “Catching prey might be difficult. But the wolf is unrelenting.”

Mr. Ren has a reputation for being blunt in conversation. In 2010, Rick Perry, then the governor of Texas, spoke at the ribbon-cutting for Huawei’s new American headquarters in Plano.