Leading US firm Chadbourne & Parke has lost its managing partner in Moscow, Robert Langer, to a rival Akin Gump Strauss Hauer & Feld.
Langer, who had been in Russia for seven years with Chadbourne & Parke, said there was no overriding reason behind the move, but a "lot of little things contributed".
He said he preferred the direction Akin Gump Strauss Hauer & Feld was taking, was impressed with its clients and believed it would be good for his clients, which include several strategic investors.
Langer's move has also prompted a New York-based colleague, Melissa Schwartz, who he worked with closely, to join his new firm's New York office.
Schwartz has been made a partner in the move and will continue to work with Langer, sharing her time between New York and Moscow.
Chadbourne & Parke has responded to the move by reinstalling Eugene Sullivan in Moscow. He originally set up the office in Russia.
New York Chadbourne & Parke partner Jerome Katz said: "We have 20 lawyers in our Russian practice - there are 13 including two partners in Moscow, five including a partner in New York and two including a partner in Washington. You can look at the numbers and draw your own conclusions."