Which security operation is performed to protect the main body while gaining time and preventing enemy observation?

The operation that is performed to protect the main body while gaining time and preventing enemy observation is the guard. The primary purpose of a guard operation is to provide security for a larger force, often by establishing a defensive position or engaging the enemy to delay or disrupt their advances. This ensures that the main body can reposition, regroup, or carry out its mission without suffering undue interference from enemy forces.

In a guard operation, units are typically deployed in a forward position to screen the main body. They engage the enemy to an extent while also being prepared to withdraw if necessary. This allows the main force to maintain its operational tempo and stay concealed from enemy observation whenever feasible.

The other options, while related to military operations, do not specifically address the need for protection and time-gaining in the same context as a guard. For instance, an interdict focuses on disrupting the enemy’s supply lines and movement rather than protecting a specific force. Occupying typically involves taking and holding positions but may not necessarily prevent enemy observation effectively. A passage of lines refers to the movement of friendly forces through positions occupied by other friendly forces and does not emphasize protection in the manner of a guard operation.