Following Russia’s invasion of Ukraine in early 2022, more than one million refugees have arrived in Germany. These Ukrainian refugees differ in many aspects from Germany’s past forced migration experiences and there exists an urgent need for sound data and information for politics, practitioners, and academics. In response, the IAB-BiB/FReDA-BAMF-SOEP study was established to provide high-quality longitudinal data following a register-based probability sample. We detail on an approach for sampling refugees in brief time, making use of two different registers—the German population register and the central register of foreigners—and discuss the quality of the final sample with respect to potential selectivity of participation in the panel. Overall, we demonstrate the benefits and feasibility of establishing register-based samples even in the context of a geopolitical crisis and the necessity of sound data within brief time horizons. We provide guidance that can be followed for similar events in the future.