Editor’s note: In the last four years, WTOP has tracked the threats, policies and vulnerabilities that have dominated the focus of national security here in the U.S. homeland and beyond.

National Security Correspondent J.J. Green traveled more than 45,000 miles to Iraq, Afghanistan, Turkey, Israel, Germany and numerous American cities and military bases covering stories about foreign conflicts, U.S. military issues, international and domestic terrorism, intelligence matters and national security policy.

More than 300 requests, through phone calls, emails were placed to current U.S. national security officials for information and interviews.

More than 100 interviews were recorded, dozens of articles were written.

More than 200 analytical debriefs were conducted.

While this series does not address every threat individually, it’s designed to present a comprehensive picture of how U.S. national security has changed in the last four years and where it is headed.

(Copyright 2012 by WTOP. All Rights Reserved.)