Coalition Systems is building the shared coordination layer for the national security ecosystem. The defense software stack is hyper-fragmented, and in the absence of purpose-built infrastructure, military units, agencies, intelligence services, and critical infrastructure coordinate on Signal, WhatsApp, and Google Sheets. None of them connected by software built for the purpose. Coalition OS fixes that. Founded by an Oxford AI Engineering PhD researcher, a critical infrastructure engineer, and a former US DoD intelligence officer. Backed by General H.R. McMaster, the former Director of the Defense Intelligence Agency, and Andreessen Horowitz's a16z Speedrun fund.