A litigation army is massing at major law firms to fight the wave of investigations, class actions and bankruptcies that are expected in the coming months — and years — in the wake of the subprime-mortgage mess.

Skadden, Arps, Slate, Meagher & Flom alone says it has roughly 100 lawyers across the firm working on subprime-mortgage fallout for clients such as Wells Fargo; O’Melveny & Myers has about 40 lawyers working for clients such as Option One Mortgage Corp. and Ocwen Federal Bank; and Kirkpatrick & Lockhart Preston Gates Ellis has roughly 50 lawyers delving into a bankruptcy investigation, led by partner Michael Missal, of subprime lender New Century Financial Corp.