It was not until the summer of 2000 that the N.S.C. realized it had stumbled on not only the most prolific arms trafficking operation in Africa, the Middle East and Afghanistan but probably the best connected (and protected) private-weapons transport and brokering network in the world. Smith and others took their information to Richard C. Clarke, then the chief of counterterrorism for the N.S.C. ''Get me a warrant,'' Clarke responded.