The Japanese were now commanded by Maj. Gen. Kensaku Oda, who succeeded General Horii, who had drowned in the Kumusi River while retreating from their initial attack across the Kokoda Track on Port Moresby. The Japanese at Buna-Gona were unable to dig deep trenches or shelters due to the water table. Instead, they built hundreds of coconut log bunkers. These had mutually supporting lines of fire and were organized in depth. The bunkers were often linked by trenches allowing the Japanese to move at will among them, reinforcing one another.