Fragile states are the toughest development challenge of our era. But we ignore them at our peril: about one billion people live in fragile states, including a disproportionate number of the world's extreme poor, and they account for most of today's wars. These situations require a different framework of building security, legitimacy, governance, and the economy. Only by securing development - bringing security and development together to smooth the transition from conflict to peace and then to embed stability so that development can take hold - can we put down roots deep enough to break the cycle of fragility and violence. Currently, we face critical gaps in our international capabilities to secure development. We need to better integrate military, political, legal, developmental, financial and technical tools with a variety of actors, from states to international organisations, civil society, and the private sector. Beyond assistance, we need new networked relationships between peacekeeping forces and development practitioners, and a new approach to security, to help the people in fragile states shift from being victims to principal agents of recovery.