What is the primary function of bridge-building units in offensive engineering?

The primary function of bridge-building units in offensive engineering is indeed to provide crossing capabilities over obstacles. In military operations, mobility is crucial, and often, forces encounter natural or man-made barriers such as rivers, ravines, or other terrains that impede their movement. Bridge-building units are specifically designed to construct temporary or semi-permanent bridges that allow troops, vehicles, and equipment to traverse these obstacles efficiently.

By establishing these crossings, bridge-building units enhance operational flexibility and ensure that forces can maintain momentum during an advance or retreat. The construction of such bridges supports logistics, enabling the timely and effective movement of supplies and reinforcements. This capability is vital for maintaining offensive operations, as it allows forces to exploit weaknesses in enemy lines and secure tactical advantages.

The other options, while relevant to military operations, do not reflect the specific purpose of bridge-building units. Creating defensive structures falls outside their primary function, as does conducting intelligence surveys or executing aerial assaults. These activities are typically performed by other specialized units within military operations.