Former senators John Breaux, left, and Trent Lott at their lobbying firm, Squire Patton Boggs, on June, 22, 2015 in Washington, D.C. (Photo by Bill O’Leary/The Washington Post)

International law firm Squire Patton Boggs will acquire the smaller California-based law firm Carroll, Burdick & McDonough, the firms announced Monday.

The deal, slated to become effective in March, will bring together Squire’s 1,500 attorneys with Carroll Burdick’s 50.

Squire’s most recently reported annual revenue, from 2014, is $870.5 million; Carroll Burdick does not report its revenue figures publicly.

In Washington, Squire Patton Boggs is best known for its lobbying practice, which it picked up in 2014 after Squire Sanders merged with lobbying powerhouse Patton Boggs. The combined firm now has the nation’s third-largest lobbying practice, earning nearly $25 million in lobbying revenue in 2015 — but lobbying earnings have declined steadily since the 2014 merger. In 2015, the firm experienced the most drastic year-over-year decline in lobbying revenue out of the top 10 firms, sliding 21 percent from $32 million to $25 million.

[A year after rocky merger, Patton Boggs aims to reestablish dominance]

The firm is currently representing embattled auto supplier Takata, which is under fire for manufacturing faulty airbag inflators that have been linked to at least 10 deaths and led to the recall of millions of airbags.

Carroll Burdick defends companies in product liability and class action litigation, as well as handling general corporate matters, and its clients include German automakers Volkswagon and Mercedes-Benz. The firm has offices in San Francisco, Los Angeles, Beijing, Hong Kong and Böblingen, Germany.

“With this combination, and the new relationships that come with it, we have even greater opportunities to better serve our clients with strong and developing global businesses,” Squire Patton Boggs Chairman Mark Ruehlmann said in a statement.

Carroll Burdick Chairman Matthew Kemner will serve as a member of Squire Patton Boggs’ board.

“As we looked to grow and expand the range of services we could offer clients … joining a firm with the scale, practice breadth and global reputation of Squire Patton Boggs was a logical step,” Kemner said.