The battle bore strong significance in the direction of the war because it might result in the total control of China by Japan or the safety of its material supply chain by China. Before the battle, China had been routed by Japan and withdrawn its military forces and civilians from the very north southwards, as well as had its capital city Nanjing falling into the hands of Japanese. China would not have afforded the loss again, it must win at any cost and that led to the heavy loss of lives in this battle of both sides.
The battle was significant because it could determine whether Japan controlled all of China or if China could protect its supply chain from them.  Before the battle, China had already been defeated and retreated southwards, with Nanjing falling into Japanese hands. This loss would have been unacceptable to China, leading to heavy casualties on both sides in order to secure victory.