Secure data transmission is essential for both training and testing environments. It has been incorporated into the U.S. NCDSMO Baseline for SABI environments since 2009 and comes with built-in support for various protocols including DIS, HLA, TENA, RTP, and MPEG2-TS, while conforming to NSA Raise the Bar and NIST standards. The High Performance Computing Modernization Program Office (HPCMPO) has assessed its compatibility with the Defense Research & Engineering Network (DREN) and Secure Defense Research & Engineering Network (SDREN). SimShield facilitates fully automated, predictable, controlled, and audited two-way communication, as well as the sanitization of events across distinct, air-gapped security domains. In contrast to Government-Off-The-Shelf (GOTS) solutions, it ensures access to the latest features without incurring additional costs. This system allows multiple national agencies or coalition forces to train simultaneously within a singular, real-world environment. Furthermore, it ensures sanitized information sharing, which accelerates the detection and resolution of issues during the Research, Development, Test & Evaluation (RDT&E) phases. Ultimately, this robust architecture enhances the overall efficiency and effectiveness of collaborative defense efforts.