"National Intelligence Estimates (NIEs) are the Intelligence Community's (IC) most authoritative written judgments on national security issues and designed to help US civilian and military leaders develop policies to protect US national security interests. NIEs usually provide information on the current state of play but are primarily 'estimative'-that is, they make judgments about the likely course of future events and identify the implications for US policy [...] We judge the US Homeland will face a persistent and evolving terrorist threat over the next three years. The main threat comes from Islamic terrorist groups and cells, especially al- Qa'ida, driven by their undiminished intent to attack the Homeland and a continued effort by these terrorist groups to adapt and improve their capabilities. We assess that greatly increased worldwide counterterrorism efforts over the past five years have constrained the ability of al-Qa'ida to attack the US Homeland again and have led terrorist groups to perceive the Homeland as a harder target to strike than on 9/11. These measures have helped disrupt known plots against the United States since 9/11." The report also included issues such as possible waning international cooperation in fighting terrorism, the current heightened threat environment in the U.S., al-Qad' ida's efforts to acquire and use chemical, biological, or nuclear material in potential attacks, and the ability of the U.S. to detect broader and more diverse terrorist plotting.