After the fall of Busan, the Japanese army had to secure their bridgehead, because ten kilometres to the north of Busan lay the fortress of Dongnae, which was situated in a very strong position atop a hill,  dominating the main road north to Hanseong.
Following the capture of Busan, the Japanese military needed to establish control over their defensive perimeter.  Dongnae fortress, located ten kilometers north and perched atop a hill, commanded the main route northward towards Hanseong.