Lockheed Martin, Thales, STN Atlas, and Raytheon were approached to provide tenders to design and assemble a new combat system for the submarines, with all four submitting proposals during early 2000. In May 2000, after the Defence Science and Technology Organisation tested operational versions of the proposed combat software packages, the Lockheed and Thales tenders were eliminated, despite the Thales proposal being rated better than Raytheon's. After indepth testing of the remaining systems and observations of the systems in action, the German STN Atlas ISUS 90-55 aboard an Israeli "Dolphin"-class submarine and the American Raytheon CCS Mk2 aboard a USN "Los Angeles"-class submarine, it was decided that the STN Atlas system was the best for the class. However, political pressure from both the United States and Australia, questions about the security problems and possible leaks involved with a European combat system linked to American weapons, and desires to increase the political and military ties between Australia and the United States resulted in the cancellation of the tender program in July 2001 and the decision to enter a joint development program with the United States, with a formal agreement signed on 10 September 2001 at the Pentagon.