On 31 July 2008, U.S. Navy acquisition officials told Congress that the service needed to purchase more s, and no longer needed the next-generation DDG-1000 class, Only the two approved destroyers would be built. The Navy said the world threat picture had changed in such a way that it made more sense to build at least eight more "Burke"s, rather than DDG-1000s. The Navy concluded from fifteen classified intelligence reports that the DDG-1000s would be vulnerable to forms of missile attacks. Many Congressional subcommittee members questioned that the Navy completed such a sweeping re-evaluation of the world threat picture in just a few weeks, after spending some 13 years and $10 billion on the development of the surface ship program known as DD-21, then DD(X), and finally DDG-1000. Subsequently, Chief of Naval Operations Gary Roughead cited the need to provide area air defense and specific new threats such as ballistic missiles and the possession of anti-ship missiles by groups such as Hezbollah. The mooted structural problems have not been discussed in public. Navy Secretary Donald Winter said on 4 September that "Making certain that we have – I'll just say, a destroyer – in the '09 budget is more important than whether that’s a DDG 1000 or a DDG 51".