Remote sensing of soil moisture has become a topic of increasing interest over the past several decades. Global monitoring of soil moisture content is a critical element in meteorological modeling, agricultural planning, disease spread monitoring, flood/landslide risk evaluation, studies of the Earth's water and carbon cycles, and many other environmental issues. While remote sensing soil moisture from radiometric measurements has a long history, the subject of inverting soil moisture from radar measurements (particularly in the presence of vegetation) is a difficult problem which remains the subject of active research. This book describes research fostering the inversion of soil moisture from radar returns using airborne and space borne instruments, particularly the Synthetic Aperture Radar (SAR), at L- band frequencies. The inversion techniques discussed herein specifically include change-detection-based and forward-model-based methods. The culmination of the research describedherein aims to benefit current and future soil moisture remote sensing techniques for L-band radar systems.