Complex sentence: Unaware of this operation, the Japanese army collapses part of the bridge to prevent Nobuo from escaping, trapping him in a tunnel while they turn on wind repulsion devices loaded with Liquid Nitrogen in an attempt to freeze him.
Split into simpler sentences: Unaware of this operation, the Japanese army collapses part of the bridge to prevent Nobuo from escaping, trapping him in a tunnel. They turn on wind generators loaded with Liquid Nitrogen in an attempt to freeze him.