The US Army V Corps and Defense Innovation Unit are seeking technologies for the Spectrum Proof IV&V event, focused on Electromagnetic Warfare capabilities to support the Eastern Flank Deterrence Initiative. The event will take place from November 2 to November 6, 2026, at Fort Knox, Kentucky, with selected technologies potentially eligible for follow-on experimentation in the EUCOM theater in 3QFY27. No budget information is specified, and the government will not reimburse any costs incurred in responding to this sources sought. Interested parties must submit a whitepaper and quad chart by July 31, 2026, with submissions evaluated for maturity and mission alignment. Technologies that demonstrate sufficient readiness may be invited to participate in the operational environment event.