CHICAGO—R-T Specialty L.L.C., the wholesale unit formed by Ryan Specialty Group, has made its first acquisition, buying Los Angeles-based Chartwell Independent Insurance Brokers L.L.C., the company said Tuesday.

Chartwell, founded in 2004 by Ben Beazley, is a national wholesale broker with expertise in property accounts, R-T Specialty said in a statement. Mr. Beazley will continue to serve as CEO and managing director of the company. Terms of the deal were not disclosed.

Ryan Specialty Group was founded in February by Patrick G. Ryan, founder and longtime CEO of Aon Corp. The firm is involved in a legal battle with Birmingham, Ala.-based CRC Insurance Services Inc. stemming from a large-scale defection in May which saw more than 120 employees leave CRC for Mr. Ryan's new wholesale venture.