This publication constitutes a Broad Agency Announcement (BAA) as described in Federal Acquisition Regulation (FAR) Part 35.016, FAR 6.102(d)(2), and DFARS 235.016. This BAA is a competitive solicitation of proposals focused on research and development of technologies to meet the mission of the Defense Threat Reduction Agency (DTRA). Formal Requests for Proposal regarding this announcement will not be issued. With this BAA, DTRA is soliciting innovative proposals for technologies in the technology readiness level (TRL) 3-7 range that will lead to new or improved technical solutions for countering and deterring WMD and other emerging threats. Amendment 1 to this BAA is posted with updates based on the 2022 DTRA Strategy for Research, Development, Test, and Evaluation. This includes update to the BAA as well as to its Attachment 5 Representations and Certifications. Addendum 1 to this BAA is posted as a research opportunity that expands on the Research & Development thrust area of “Control, disable, and defeat current and emerging WMD threats”. This addendum is open and in effect starting with date of posting through 2 June 2023 (the final date for Phase I submissions). Addendum 1 Revision 1 to this BAA is posted to extend the final date for Phase I submissions to 16 June 2023. This is extended as no proposals were received to date for this addendum. Addendum 2 to this BAA is posted and serves to supplement the Defense Threat Reduction Agency's (DTRA) Research and Development Innovations Broad Agency Announcement (BAA), HDTRA1-22-S-0003. This research opportunity expands on the Research & Development thrust area of “understand current and emerging WMD situations, threats, and capabilities”. This addendum is open and in effect from 7 January 2025 (starting with date of posting) through 4 February 2025 (the final date for Phase I submissions). Addendum 2 Questions and Answers posted 4 February 2025 Amendment 2 is posted to bring the BAA current with organizational updates and mission objectives. Addendum 3 serves to supplement the Defense Threat Reduction Agency's (DTRA) Research and Development Innovations Broad Agency Announcement (BAA), HDTRA1-22-S-0003. This research opportunity expands on the Research & Development thrust area of “enable effective and integrated WMD deterrence”. This topic is open and in effect from 31 July 2025 (starting with date of posting) through 29 August 2025 (the final date for Phase I submissions). Addendum 3 Amendment 1 extends the required date for Phase I submissions from 29 August 2025 to 19 September 2025. Please also see attached Questions and Answers to this Addendum topic.