Which of the following refers to a defensive position established during military operations?

A defensive position established during military operations is commonly referred to as a strong point. This term indicates a fortified location designed to provide an enhanced defensive capability. Strong points are strategically selected and constructed to create a more robust position that can resist enemy attacks, support friendly units, and provide an observation point for intelligence gathering.

The chosen strong point typically benefits from natural terrain features and additional fortifications, allowing it to serve as a focal point for defensive operations. Such positions can significantly influence the outcome of engagements by providing advantageous fields of fire, shelter for troops, and a secure area from which to launch counterattacks.

In contrast, the other options do not specifically denote defensive positions. A light machine gun refers to a type of weapon used in combat rather than a defensive location. An air defense gun is focused on protecting against aerial threats and does not imply a fortified position. The forward line of troops refers to the frontline of military units engaged with the enemy, which may not be as fortified or strategically reinforced as a strong point.