Insignia Description
A silver color metal and enamel device 1 1/16 inches (2.70 cm) in height overall consisting of a double webbed silver key, vertical with bow in base bearing a black ermine spot all between two silver fleurs-de-lis on a blue area enclosed by two silver lightning flashes arced from web to bow all above a curved scarlet scroll inscribed “SILENTLY WE DEFEND” in silver.

Symbolism
Oriental blue and silver (gray) are the colors associated with Military Intelligence and a key is emblematic of authority and security. The double web and flashes represent the unit’s concern for both overt and covert security communications. The flashes also denote celerity in operation procedures, as well as allude to the unit’s Signal lineage. Initially designated the 3118th Signal Service Battalion, the unit participated in the Northern France, Rhineland and Central Europe campaigns, World War II, represented by the fleurs-de-lis and ermine spot. The scarlet scroll denotes the Meritorious Unit Commendation Streamer awarded the unit for service in the European Theater.

History
The distinctive unit insignia was originally approved for the 502d Army Security Agency Group on 26 July 1972. Effective 1 July 1981, it was redesignated for the 502d Army Security Agency Battalion. The insignia was redesignated with the symbolism amended for the 204th Military Intelligence Battalion on 19 March 1987.

Source: The US Army Institute of Heraldry