This paper describes a novel network security appliance -- the Tactical Smart Network Interface Card (TSNIC) — that leverages state-of-the-art Field Programmable Gate Array (FPGA) technologies to continuously maintain the integrity of tactical missions. The Smart NIC appears as an all-hardware “bump- in-the-wire” along any network segment or attached to an industry standard bus interface providing infrastructure defense for ground vehicles. It can be custom configured to provide encryption, protocol and file format validation, and/or protocol encapsulation. These capabilities are achieved by several innovations: high-level synthesis (HLS) for rapid circuit development, automated parser generation to adapt to mission requirements, and a hardware nano-marshal to dynamically adapt defensive posture in the face of changing threat profiles.