The 158th RCT, acting upon new instructions from Sixth Army, turned its energies to clearing the rest of the Bicol Peninsula and to gaining contact with XIV Corps, which Sixth Army had directed to start driving into the peninsula from southern Luzon. Without waiting for the 2d Battalion to return from the Sorsogon Peninsula, the remainder of the 158th RCT, on 11 April had struck toward Camalig from Daraga, employing Routes 1 and 164 as axes of advance. Troops along Route 164 bypassed the Japanese defenses at the Cituinan Hills to the north and entered Camalig unopposed on the afternoon of the 11th.
Since the Japanese in the Cituinan Hills posed a threat to the 158th RCT’s line of communication back to Legaspi, General MacNider felt that an advance in strength beyond Camalig before reducing the Cituinan defenses would overreach the bounds of a calculated risk. Accordingly, on 12 April, the 1st and 3d Battalions, 158th Infantry, attacked into the hills. Slowed by thick jungle and rough terrain almost as much as by the Japanese, and constantly harassed by night attacks, the two battalions had not overrun the defenses when, on 19 April, the 2d Battalion returned from the Sorsogon Peninsula to join the fight. Progress continued to be painfully slow, and it was not until 28 April that organized Japanese resistance finally collapsed. The task of clearing the Cituinan Hills cost the 158th Infantry approximately 40 men killed and 235 wounded; the Japanese lost almost 700 men killed in the region.Although the 158th RCT did not know it, the reduction of the Cituinan Hills marked the end of large-scale organized resistance on the Bicol Peninsula, where no more than 1,400 Japanese remained alive as of the end of April. On the 29th the main body of the 158th began moving northwestward from Camalig, following a reinforced company that had reached Iraga, twenty-five miles distant, on 14 April. Rapidly, the regiment overran potentially strong enemy positions in excellent defensive terrain as the remaining Japanese, demoralized, offered only token resistance before melting away into hills on either side of Route 1. On 2 May patrols of the 158th Infantry established contact with the 5th Cavalry at barrio San Agustin, on Route 1 fifteen miles northwest of Iriga.Troops of the 1st Cavalry Division had begun moving onto the Bicol Peninsula on 12 April, when they relieved units of the 11th Airborne Division at Atimonan. The next day the 5th Cavalry struck east from Atimonan and on the 14th reached Calauag, thirty miles away.
All the way from Atimonan to Calauag, Route 1 was in poor condition and beyond Calauag supply movements were almost impossible. The speed of advance now hinged on the speed of engineer road and bridge repairs. Accordingly, the 5th Cavalry secured the eastern shore of Tayabas Bay and set up a supply point at the bay’s northeastern corner so that LCM’s could bring forward ammunition, food, and equipment from Batangas. Beginning on 27 April the main body of the regiment began moving by LCM across Ragay Gulf, the first indentation on the south coast of the Bicol Peninsula beyond Tayabas Bay. On the 28th the regiment, encountering no resistance, moved from the shores of Ragay Gulf to Naga, eight miles northwest of barrio San Agustin, and had no trouble marching south to meet the 158th Infantry.
Guerrillas had informed XIV Corps, which acquired control of the 158th RCT on 22 April, that a Japanese force of some 2,500 men was dug in along the slopes of Mt. Isarog, an extinct volcano centering eight miles northeast of San Agustin. This report the 5th Cavalry and 158th Infantry proved false in a series of patrol actions between 2 and 15 May. The next day, the 16th, General MacNider radioed to General Griswold that the Bicol Peninsula was secure and that no signs of organized Japanese resistance remained.
The two regiments continued patrolling for some weeks until, on 6 June, the 5th Cavalry returned to southern Luzon. The 158th RCT busied itself with the problem of reorganizing and equipping guerrilla forces and in mid-June turned over responsibility for further mopping up to the Filipinos. To that time the operations to clear the Bicol Peninsula had cost the U.S. Army units involved approximately 95 men killed and 475 wounded. The Japanese had lost over 2,800 killed and 565 captured, including 350 Formosan labor troops whom the Japanese Army had left to fend for themselves.
The strategic goal of the Bicol Peninsula operation–to finish clearing the Visayan Passages–had been realized on 2 May with the contact between the 158th Infantry and the 5th Cavalry at San Agustin. The final patrolling and mopping up the two regiments undertook had provided the necessary capstones to the combined Sixth Army-Eighth Army campaign to assure the safety of the Visayan Passages for Allied shipping.
Undertaken against generally ill-equipped, poorly fed, second-class and third-class Japanese forces, the campaign had yet proved costly. U.S. Army units involved had lost roughly 300 men killed and 1,130 wounded; the Japanese, to mid-June, had lost at least 8,125 killed and nearly 750 captured. The campaign had proved logistically more important than it had strategically or tactically. Sixth Army, Eighth Army, and Allied Naval Forces had not found the Japanese coast artillery and mine fields they had expected to discover emplaced so as to endanger Allied shipping in the passages. Nevertheless, General MacArthur would ultimately have had to direct his subordinate echelons to eliminate the Japanese from southern Luzon, the Bicol Peninsula, northern Samar, and the islands of the inner passages if for no other reason than to liberate from the Japanese yoke the many thousands of Filipino inhabitants of those regions and to restore to the Filipinos their lawful government…
Pictured: Arizona’s 158th RCT lands at Legaspi…