[en] In May 2011, a workshop was held to develop broader awareness of the technical and operational challenges that could be used to enhance effective transparency and/or verification in the medium to long-term. Building confidence in a broader multi-lateral engagement scenario adds even greater challenges than the traditional bi-lateral approaches. The multi-disciplinary group that attended included decision-makers needing to understand present and possible future technical capabilities, and the technical community needing clearer definition of possible requirements and operational constraints. In additional to traditional presentations, the group conducted an exercise to stimulate new perspectives on verification requirements for a scenario based on nuclear arms reductions at very low numbers of nuclear weapons. The workshop participants were divided into two groups and asked to explore the political and technical requirements needed for States to move towards significant arms reductions. Using a technique called 'back-casting' participants were asked to imagine a world without nuclear weapons and describe what would be needed to achieve levels of one thousand, one hundred, ten, and ultimately zero weapons in the world. Most participants agreed that a strong political commitment will be necessary and that complete disarmament will only be possible if states are convinced that nuclear weapons serve no purpose. Both groups believed that a time period of greater instability would be encountered when moving from 1000 to 100 nuclear weapons and that it would be imperative to accelerate quickly through this period. The group discussed the need to have an international body monitor the disarmament process to maintain legitimacy for the international community. One possibility could be the development of an intergovernmental panel on verification and disarmament to monitor and facilitate disarmament. The groups recognized the problem of fissile material disposition after warheads dismantlement. Controlling fissile materials is important since nuclear material could be a direct route to reconstitution of weapons. (A.C.)