The terrain that the troops traversed was adapted to defensive fighting, and the 1st [Japanese] Division took full advantage of this fact. There were deep ravines and steep hills where the enemy had dug in on both the forward and reverse slopes. The entire area was covered by heavy rain forest with dense underbrush. The nearly constant rainfall made observation difficult and the maps for the area were very inaccurate. (Cannon 325)
John Toland, The Rising Sun: The Decline and Fall of the Japanese Empire, 1936-1945