As the Cold War drew toward an end in 1989, and the Berlin Wall finally came down, there was still a feeling of distrust among the former adversaries of the East and West. In 1992, a major barrier in this distrust was lifted when 27 nations signed the Treaty on Open Skies. This unprecedented display of openness has allowed former military enemies to conduct aerial observations over each other's territories. Although the treaty has yet to enter into force (as of this writing), it has already proven successful through the benefit of joint trial flights. President George Bush assigned the oversight and implementation of this treaty to the On-Site Inspection Agency (OSIA). On October 1, 1998, OSIA was disestablished, and it's functions transferred under the control of the newly-created Defense Threat Reduction Agency (DTRA). However, from a mission standpoint, nothing has changed in how the Open Skies Treaty is implemented. Under DTRA, the On-Site Inspection Directorate, and furthermore the Open Skies Division, continues to oversee the treaty on behalf of the United States. We hope that you enjoy reading and learning about "The Treaty on Open Skies." C. Duane Heughan Captain, U.S. Navy Chief, Open Skies Division