On Monday, John Z. Huang was managing partner of a three-lawyer office at 300 W. Adams St. that served as the Chicago outpost for the largest law firm in mainland China, 4,000-lawyer Dacheng Law Offices.

On Tuesday, he became a member of the world’s new largest law firm, Dentons, whose 135-lawyer Willis Tower office across the street less than five years ago was branded Sonnenschein, Nath & Rosenthal.

In its latest and most historic step to becoming the largest firm, Dentons announced Monday night its merger with Dacheng — the first official tie-up between a large global firm and a Chinese firm — creating a brand with more than 6,500 lawyers and professionals in 120 locations.

“It hasn’t been a question of if a trans-Pacific combination would happen but when, and it’s happening now,” said Kent Zimmermann, a consultant at the Zeughauser Group.

“It’s the biggest news the legal industry has seen in a long time. For any firm that’s global or aspires to be global, China is too big a market to ignore.”

The move underscores the importance of the Chinese economy and legal market for major law firms. As the world’s second-largest economy continues to grow at an envious pace, Chinese businesses are also encountering new legal needs that put U.S. and international lawyers in demand.

For instance, China’s outbound investments last year outpaced the inbound flow of capital for the first time, suggesting Chinese firms will need local counsel in foreign countries where they increasingly invest.

“All of our competitors are looking East,” Elliott Portnoy, who will be global CEO of the new firm, said in a statement.

“By uniting East and West in one firm — not merely through a few offices in large cities, but with a deep presence across China — we can provide Chinese businesses with global ambitions and international clients with interests inside China a reach and depth that simply can't be found elsewhere.”

Firm leaders were not available for comment by early this afternoon. Dentons’ local office managing partner is Mary G. Wilson.

Dentons has about 2,600 lawyers and professionals worldwide and last year recorded revenue of $1.26 billion, according to The American Lawyer. Created by a three-way merger in March 2013, Dentons employees still send e-mails with a tagline announcing the event: “SNR Denton is proud to join Salans and FMC as a founding member of Dentons.”

Dacheng was co-founded in 1992 by Peng Xuefeng, who is based in Beijing, still serves as the firm’s director and will be the chairman of the new firm’s global board. Dacheng, which is significantly larger than Dentons, took in revenue around $400 million last year. On a per-lawyer basis, the Chinese firm’s revenue is a fraction of its new partner.

The new firm will actually be five separate financial entities in a structure known as a verein, an increasingly common setup for global firms. The main benefit of the verein structure is that it allows profit from various regions to remain separate, so, for instance, a less profitable region won’t affect recruiting partners in a more profitable market.

For clients, the firm stressed the benefit of the merger as creating “the only firm to offer seamless service” across basically the entire globe, including “all 34 of China's regional administrative divisions.”

The deal requires approval by Chinese regulators, which is indicative of a legal market and economy under significantly more government oversight than in America. Foreign law firms have faced significant regulatory barriers in China, including a restriction on hiring lawyers with active Chinese legal licenses.

With those barriers in place, some domestic Chinese firms have grown at a pace reminiscent of U.S. law firms a decade or more ago.

In 2002, only “a handful” of Chinese law firms had more than 100 lawyers, according to a 2012 Fordham Law Review article. By 2011, more than a dozen firms had 200 or more lawyers, and Dacheng had already earned the distinction of the largest firm in China with more than 2,000 lawyers.

The new firm will have five regions: Asia, Canada, Europe, the United Kingdom and the Middle East (UKMEA) and the U.S.

Each will be led by a regional CEO, Dentons said in a statement. The U.S. region is technically Dentons US LLP.

A 19-member global board will be comprised of 14 members from Dentons and five from Dacheng, the firm said. The firm logo features the Chinese characters that translate to “Dacheng” followed by “Dentons,” spelled in white and outlined by the firm’s familiar purple.

Other large firms with a Chicago presence have sought to export their brand to China.

Baker & McKenzie LLP, previously the world’s largest firm with about 4,200 lawyers, has practiced in China for nearly 40 years. It has more than 300 lawyers in offices in Hong Kong, Beijing and Shanghai.

DLA Piper also has a significant Chinese practice with offices in those same cities.

McDermott, Will & Emery LLP is “strategically aligned” with MWE China Law Offices, a seven-partner practice based in Shanghai that was hailed as “groundbreaking” when it launched in 2007. That same year, Mayer, Brown LLP combined with Johnson, Stokes & Master, a Hong Kong firm with more than 250 lawyers at the time, to create Mayer, Brown JSM.

Even so, consultants said the Dentons-Dacheng merger represents a new strategy for international firms seeking a presence in mainland China — and for Chinese firms to expand their influence around the globe.

“I think it’s a big deal,” said Bruce MacEwen, a law firm consultant and author of the blog “Adam Smith, Esq.”

“Whether it ends up being wildly successful or unsuccessful, I think it says something very important about the way that certainly one major player sees the world evolving.”

For lawyers in Chicago, there are more practical concerns.

It is unclear if or when Dacheng partner Huang and associates Iskra G. Panteva and Jenna Smith will move across the street to Dentons’ Willis Tower office, where its lease of up to 144,000 square feet runs through 2029.

“As we move towards a full launch this spring, we will be rolling out our plans for office integration in cities where both firms have offices,” Lisa Sachdev, a Dentons spokeswoman, said in an e-mail. She could not say exactly how many lawyers will work at the new firm, but it appears to be about 6,600.

The Dentons news represents the second announced merger for a Chicago office in as many days. On Monday, Ungaretti & Harris LLP’s more than 100 lawyers were acquired by Nixon, Peabody LLP, a 600-plus lawyer firm with 16 offices, including Shanghai and Hong Kong.