This comprehensive analysis of COVID-19 draws on the Iceberg Framework--a modified systems thinking model--to examine the deeper forces that shaped the pandemic's trajectory, from structural inequities and institutional fragility to shifting mental models and global behavioral patterns. Authored by a former Taiwanese Minister of Health and an experienced health system leader, the book combines personal insight with international perspective, offering historical context, contemporary data, and strategic foresight. It situates COVID-19 among history's deadliest pandemics while critically exploring the events, systemic structures, and cultural responses that influenced the crisis. Structured in four parts, the book journeys from echoes of past pandemics and variant-driven disruptions to the hidden foundations of public health responses, culminating in a forward-looking reflection on how COVID-19 has reshaped our understanding of pandemic risk and resilience, while also offering readers a framework for enhanced preparedness in an era of converging global threats. Timely, accessible, and analytically rigorous, Decoding the Pandemic is essential reading for students, researchers, and practitioners in public health, epidemiology, global health policy, and systems science--anyone seeking to understand not just what happened, but why, and what must change before the next pandemic arrives.