An international crackdown on shipments of weapons of mass destruction is yielding results, a senior Pentagon official told reporters today. In addition to tangible successes like the seizure last October of a Libyan-bound ship carrying nuclear centrifuge equipment, the Proliferation Security Initiative is providing interdiction experience to world militaries through multinational exercises, the official said. A weeklong naval exercise in the Arabian Sea is due to culminate Jan 16 and Jan. 17, when Spanish special operations forces are scheduled to...