In the space of a week there have been two significant raids by U.S. firms on other U.S. firms in the City.

A recent survey showed that hiring by US firms in London fell to its lowest level since 2004 last year. And associate headcount took a dive across the board during 2009, with overall numbers dipping from 2,536 to 2,214 by January 2010. But that hasn’t stopped some firms opting for alternative expansion plans.

Rather than seeking out and taking on fresh talent from the heaving job-seekers market, Morgan Lewis has pilfered the entire London employment department of Dewey & LeBoeuf reports the Lawyer. And Roll on Friday reports this morning that six banking associates were turfed out of White & Case after resigning en masse, apparently headed for Latham & Watkins (at least five of them anyway). Which puts them hot on the heels of four partners that left the firm for Latham & Watkins in January.

Perfect sense really. Recessions are all about increasing market share; what easier way than to pinch whole teams from your rivals.