Due to the wide variety of Army forces' missions across the full range of military operations, the term "adversary" is often used in this paper in lieu of enemy. The term enemy is reserved to indicate adversaries engaged in lethal operations against U.S. forces.
In cryptography, an adversary (rarely opponent, enemy) is a malicious entity whose aim is to prevent the users of the cryptosystem from achieving their goal (primarily privacy, integrity and availability of data). An adversary's efforts might take the form of attempting to discover secret data, corrupting some of the data in the system, spoofing the identity of a message sender or receiver, or forcing system downtime.
The Adversary is a fictional character, a demonic supervillain in the Marvel Comics universe, and one of the most powerful villains to ever appear. He first appeared in Uncanny X-Men #188, by Chris Claremont and John Romita, Jr.
In computer science, an online algorithm measures its competitiveness against different adversary models. For deterministic algorithms, the adversary is the same, the adaptive offline adversary. For randomized online algorithms competitiveness can depend upon the adversary model used.