This book investigates how development institutions created and promoted marketized development financial instruments to increase the speed and scope of assistance by leveraging private financial markets for development objectives. To attract private investors, donor governments agreed to bear the risk in these new instruments in order to mobilize investment during times of political crisis. In particular, this book contends that Germany's KfW played an outsized role in the development of these new financial instruments, particularly in microfinance banks and structured funds, as KfW's unique institutional attributes and strong political support from the German government at critical junctures fostered financial innovation. Using over 70 interviews and a cache of newly released archival materials, this books documents how KfW and other development institutions created and promoted these marketized development financial instruments, and how they have become a pillar of modern development policy.