Complex sentence: The bridge allows heavier vehicles to cross the river driving through only shallow water, and they are difficult to spot from the air and if spotted are difficult to knock out with air strikes as the water protects the bridge from blasts.
Split into simpler sentences: The bridge allows heavier vehicles to cross the river driving through only shallow water, and they are difficult to spot from the air. Even if spotted, they are difficult to knock out with air strikes as the water protects the bridge from blasts.