Clichés aside, sometimes law really is a relationship business. Consider Kirkland & Ellis’s role in Teva Pharmaceutical Industries Limited’s $6.8 billion acquisition of Cephalon, Inc., the biggest M&A deal of the year involving the United States and an emerging market.

Kirkland had long represented Teva, which is based in Petah Tikva, Israel, in litigation matters, but for transactions, Teva more commonly turned to Willkie Farr & Gallagher. For instance, when Teva acquired Montvale, New Jersey’s Barr Pharmaceuticals, Inc., for $7.5 billion in 2008, Willkie was Teva’s primary outside counsel.