a threat to the United States and our allies," a Pentagon statement said. Syria has been identified as a host for Short Range Ballistic Missiles (as it acquires equipment from North Korea and Iran). Categories MDA divides its systems into four phases: boost; ascent; mid-course; and terminal. Each of these corresponds to a different phase of the threat ballistic missile flight regime. Each phase offers different advantages and disadvantages to a missile defense system (see missile defense classified by trajectory phase), and the geography of each defended area dictates the types of systems which can be employed. The resultant flexible and layered defense approach concept is believed to improve overall defense effectiveness. The more opportunities a system has to neutralize a threat (e.g., by shooting down a missile), the better the chance of success. Activities have also been categorized as fulfilling the goals of one of five "blocks". For example, "block 4.0" was stated as "Defend Allies and Deployed Forces in Europe from Limited Iranian Long-Range Threats and Expand Protection of U.S. Homeland". It included the US missile defense complex in Poland to be constructed, and the European Mid-course Radar (EMR), currently located at the Ronald Reagan Ballistic Missile Defense Test Site at Kwajalein Atoll, which was to have been modified and relocated to the Czech Republic. On 17 September 2009, the Obama administration scrapped the "block 4.0" plan, in favor of a new so-called "European Phased Adaptive Approach" (EPAA). Boost phase Can intercept all ranges of missiles, but the missile boost phase is only from one to five minutes. It is the best time to track the missile because it is bright and hot. The missile defense interceptors and sensors must be in close proximity to the launch, which is not always possible. This is the most desirable interception phase because it destroys the missile early in flight at its most vulnerable point and the debris will typically fall on the launching nations' territory. Ascent phase This is the phase after powered flight but before the apogee. It is significantly less challenging than boost phase intercepts, less costly, minimizes the potential impact of debris and reduces the number of interceptors required to defeat a raid of missiles. Midcourse phase This phase begins after the booster burns out and begins coasting in space. This can last as long as 20 minutes. Any debris remaining will burn up as it enters