The Department of Defense, through the Army Combat Capabilities Development Command (DEVCOM) C5ISR Center, is issuing a Request for Information (RFI) to identify advanced technologies and techniques for Navigation Warfare (NAVWAR) Electromagnetic Support (ES). The primary objective is to gather insights on systems that are at Technology Readiness Level (TRL) 4 and above, utilizing radio frequency (RF) techniques to detect and locate emitters while ensuring the protection of positioning, navigation, and timing (PNT) systems in a complex, contested environment. This RFI is crucial for enhancing the U.S. Army's operational capabilities and will inform future research and development efforts, potentially leading to competitive solicitations or small business set-asides. Interested parties are encouraged to submit their responses, which should not exceed 20 pages, within 30 days to the designated email address, with classified submissions accepted as necessary.