Launching a general offensive on 9 April, the three regiments drove slowly into rugged terrain where the Japanese had every defensive advantage. Kono's men had prepared cave and bunker positions, most of them mutually supporting and many connected by tunnels or trenches. The Japanese had dug tank traps along all roads and trails in the mountains, and had also laid mine fields using aerial bombs. Kono's men had excellent observation, for most of the hills in their last-stand area were open, grass covered, and steep sided. During daylight, the Japanese were content to conduct a static defense, but they undertook harassing attacks almost every night.

Little purpose can be served by describing in detail the mountain fighting in northern Negros.* The battle soon degenerated into mountain warfare of the roughest sort involving all the problems, frustrations, delays, failures, and successes that American troops were encountering in the mountains of Luzon. The 40th Division employed air and artillery support liberally,¹⁰ **but in the end, as on Luzon, had to close with each individual Japanese position with flame throwers and the rifle-carrying infantrymen. As the campaign wore on, weather also became a factor with which the 40th Division had to reckon, for dense fogs and heavy rains slowed all operations.

By 2 June the 40th Division had overrun almost the last strong, organized Japanese resistance in northern Negros. On the 4th General Kono, realizing that his remaining forces were incapable of further sustained effort, directed a general withdrawal deep into the mountains behind his broken defensive lines. The surviving Japanese dispersed into small groups seeking food and hideouts and trying to avoid contact with Abcede's guerrillas who, under the direction of the 503d Parachute RCT, took over responsibility for the pursuit of Kono's men. On 9 June the 503d relieved all elements of the 40th Division in northern Negros. By that date the Japanese had lost over 4,000 men killed. Kono lost another 3,350 troops, mainly from starvation and disease, before the end of the war. After the general surrender in August 1945, over 6,150 Japanese came down from the mountains to turn themselves in, joining about 350 others who had been captured earlier. In all, about 7,100 Japanese lost their lives in northern Negros, pinning down the equivalent of an American infantry division for over two months. The 40th Division's casualties for the operation, including those of the attached 503d Parachute RCT, totaled approximately 370 men killed and 1,035 wounded.