The Song navy was of great importance during the consolidation of the empire in the 10th century; during the war against the Southern Tang state the Song navy employed tactics such as defending large floating pontoon bridges across the Yangtze River in order to secure movements of troops and supplies. There were large ships in the Song navy that could carry 1,000 soldiers aboard their decks, while the swift-moving paddle-wheel craft were viewed as essential fighting ships in any successful naval battle.