What is the primary purpose of a machine gun in a military context?

The primary purpose of a machine gun in a military context is to provide sustained automatic fire. This capability allows a machine gun to unleash a continuous stream of bullets over an extended period, making it an essential support weapon for infantry units. Its design enables rapid fire, creating a high volume of suppressive fire that can effectively engage enemy forces, cover advancing troops, or defend positions. This feature is particularly useful in establishing dominance over the battlefield, as it can deter enemy movement and contribute to the overall tactical objectives of a military operation.

In contrast, engaging in long-range sniper operations relates to precision shooting with rifles designed for accuracy rather than the volume of fire. Serving as a marksmanship training weapon focuses on teaching shooting skills rather than fulfilling the role of a battlefield weapon. Functioning as a portable air defense system addresses a different tactical requirement altogether, targeting aerial threats rather than ground engagements where the sustained fire of a machine gun excels. Thus, the correct answer aligns with the machine gun's established role in delivering continuous, automatic fire support in military operations.