In 1997, two expansion packs for Red Alert were released for the PC, Command & Conquer: Red Alert: Counterstrike and Command & Conquer: Red Alert: The Aftermath. The expansion packs were designed by Westwood Studios with the "apprenticeship" of Intelligent Games, a London-based game developer. Much of the development on multiplayer maps was undertaken by players from the Compuserve Red Alert ladder. New units, missions, maps, and music were included in the expansions.

By October 1997, Counterstrike had sold 650,000 copies worldwide after its launch in April of that year. According to Westwood, this made it the all-time fastest-selling expansion pack for a computer game by that point. The Counterstrike add-on included the secret Ant Missions titled "It Came from Red Alert", where the player battles against an army of giant, mutant ants.
Based on the below text, which expansion pack for Red Alert featured the player fighting an army of mutant ants?
The Counterstrike add-on to Red Alert featured missions against giant mutant ants.