Joseph Andrew couldn't curb his enthusiasm. It was a frigid morning in New York, days ahead of the Jan. 26 ceremony in which Dentons tied the knot with Dacheng, China's largest firm. Andrew, Dentons' voluble global chairman, jogged to a PowerPoint slide highlighting the soon-to-be combined firms' 120 locations and pointed to the 43 dots inside China, Dacheng's major contribution to the combination.

The logic of such a deal, Andrew told a reporter, was evident. “In each of these Chinese cities, significant enterprises are being born, none of which are content to do business only in China. Getting to them first gives us a chance of winning that new business,” he said.

By more than doubling its global head count and giving it overnight heft in a country where Western firms have struggled, Dentons' China play has triggered awe—or, perhaps, fear—among rivals, whose own moves in China have been tentative. “Gobsmacked” is how Mark Herrmann, chief litigation counsel for Aon plc, described himself upon hearing the news; if you were a firm leader who was being honest with himself, he quipped in a column on Above The Law, “your heart skipped a beat when you considered that Dacheng-Dentons beat you to a critical punch.”