The modern on-site inspection (OSI) regimes developed since the conclusion of the Intermediate Nuclear Forces (INF) Treaty have added new elements to the verification structures of arms control agreements, significantly increasing their effectiveness. By permitting the on-site presence of trained inspectors and the use of specialized verification equipment to help verify compliance with the provisions of an agreement, they increase the chance that illegal activity will be discovered and complicate and significantly raise the costs of cheating. They also contribute in a major way to military openness and transparency in the areas where they are applied, reducing the possibilities of misunderstanding and mistakes in interpreting military actions. In addition, the verification regimes containing OSI establish important internationally recognized norms that provide a stronger legal and political basis for a concerted response by an individual country or collectively by the international community should violations be found.
At bottom, however, OSI regimes are only an investigative tool. They are not—and do not purport to be—watertight assurances of compliance. Even the most carefully constructed OSI regimes can be “spoofed” by a country determined on cheating and prepared to expend the necessary resources to carry out covert activity. OSI regimes, therefore are not, and should not be viewed as, a panacea for ensuring full and complete compliance with bilateral, regional, or global arms control agreements.
All OSI regimes entail a varied mix of benefits, costs, and risks—all of which must be considered in evaluating their desirability and relative effectiveness. As arms control agreements with ever more intrusive verification regimes come online, there is a need to carefully balance the contributions of each regime with its real and potential costs. Such a balanced assessment becomes particularly essential when evaluating the benefits of implementing, funding, and supporting additional OSI activities at both the national and multinational level against