Which of the following is a potential threat during an air assault operation?

In the context of an air assault operation, surface-to-air missiles pose a significant threat to aviation units. These weapons are specifically designed to target and engage aircraft, making them a critical concern for Army aviation during such operations. The environment in which an air assault takes place is often contested, and the presence of enemy surface-to-air missile systems can severely limit the effectiveness of aviation assets. Understanding this threat is essential for mission planning, as it impacts routes, tactics, and the level of escort or support needed to ensure the safety of the aircraft and personnel involved in the operation.

While hostile naval forces, cyber warfare, and underground resistance movements can also pose risks in various operations, they are not as direct or immediate a threat to the helicopters or fixed-wing aircraft during the actual phase of an air assault. Surface-to-air missiles require specific avoidance and countermeasures, thus highlighting their importance in this specific context.