Luzon
Shortly after its operations in Leyte ended, the division was notified that it was destined for combat in Luzon, to the north of Leyte. There, the 511th Parachute Infantry Regiment would make its first combat jump, with the 187th Glider Infantry Regiment and the 188th Glider Infantry Regiment making an amphibious assault to secure a beach-head for reinforcements. On 27 January, the 187th and 188th GIR set sail for Luzon, while the 511th flew by C-46 Commando transport aircraft from Leyte to Mindoro. Then, at dawn on 31 January, the two Glider regiments landed in naval landing craft near Nasugbu in southern Luzon; after a short naval barrage and strafing by A-20 Havoc light bombers and P-38 Lightning fighter aircraft, they secured a beach-head against light Japanese resistance. The 188th rapidly advanced and secured Nasugbu, with its 1st Battalion advancing up Highway 17, a major highway in Luzon, to deny the Japanese forces any chance to set up defenses. Simultaneously, the regiment's 2nd Battalion advanced south and secured the right flank of the division after crossing the River Lian. By 10:30 am the 188th had advanced deep into southern Luzon, allowing the 187th to come ashore and relieve those units of the 188th that had secured the right flank of the division. By 2:30 pm, the 188th had reached the River Palico and secured a vital bridge over the river before it could be destroyed by Japanese sappers. It then continued its advance by following Highway 17 to Tumalin, where it encountered heavier Japanese resistance.
The 188th continued to advance against increasing Japanese resistance until midnight, when the 187th took over the lead; the 188th then followed the 187th, the two units resting briefly before coming to the Japanese main line of resistance. This consisted of a series of trenches, linked to a number of bunkers and fortified caves manned by several hundred infantry and numerous artillery pieces. At 09:00, the 188th launched an attack on the Japanese line and managed to break through by midday, spending the rest of 1 February mopping up resistance in the area. On the morning of 2 February, another attack was launched, breaking a second Japanese line of defense and pursuing the retreating Japanese troops. By midnight, the 188th had breached a third Japanese line, and the divisional reconnaissance platoon had reached an area near Tagaytay Ridge where the 511th PIR was scheduled to conduct its airborne operation.
The airborne operation was scheduled for 2 February, but was rescheduled for 3 February due to continued Japanese resistance slowing the progress of the two Glider regiments. Maj. Gen. Swing only wanted the operation to go ahead if the Glider regiments were in range to provide assistance to the 511th if Japanese resistance was heavier than expected. Due to there only being forty-eight C-47 Dakota transport aircraft available, the regiment was forced to conduct the airborne operation in three lifts. The regimental staff, the regiment's 2nd Battalion and half of its 3rd Battalion would be dropped first. The rest of the regiment would be dropped second, and then the 457th Parachute Field Artillery Battalion would be dropped in the third lift.
At 03:00 on 3 February, the troops of the first lift entered their transport planes, and at 07:00 the first transports took off, protected by an escort of P-61 Black Widow night fighters, flying over Mindoro and eventually following Highway 17 all the way to Tagaytay Ridge. The ridge itself was an open space some two thousand yards (1,829 m) long and four thousand yards (3,657 m) wide, plowed in places, and had been mostly cleared of Japanese troops by local Filipino guerrillas. At 08:15 the first echelon of the first lift, approximately 345 men, successfully dropped onto the drop zone, although the second echelon, consisting of approximately 570 men, were dropped prematurely and consequently landed about eight thousand yards (7,315 m) east of the drop zone. The second lift also encountered problems with accuracy, with some 425 men dropping correctly but another 1,325 dropping early due to pilot error and poor jump discipline. Despite these problems, however, the entire regiment was assembled within five hours of the first lift landing in the drop zone. After fighting against minor Japanese resistance, by 15:00 the 511th had made contact with the 188th and 187th, and the entire division was once again assembled as a single formation. After clearing the ridge of any remaining Japanese defenders, the division began to advance towards Manila, reaching the Paranaque River by 21:00 on 3 February and encountering the beginning of the Genko Line, a major Japanese defensive belt that stretched along the southern edge of Manila This defensive belt consisted of approximately 1,200 blockhouses between two and three stories deep, many of which had naval guns or large-caliber mortars embedded within them, as well as entrenched large-caliber anti-aircraft weapons, machine-gun nests and booby-traps consisted of rigged naval bombs. The entire line was manned by some 6,000 Japanese soldiers.
The division was ordered to breach the Genko Line and drive into Manila, linking up with other American forces attacking the city from the north. All three of the divisions regiments were committed, and they began their advance on 5 February, managing to break through the defensive line despite fierce resistance by Japanese units manning it. The 511th had led the assault and broken through the Genko Line, but was soon replaced as the division's spearhead by the 188th; the glider regiment advanced westwards towards Manila in the face of heavy opposition as the 511th attempted to move into the city from the north. By 11 February, the division had penetrated as far as Nichols Field, an airfield forming the center of the Genko Line, heavily fortified with a number of entrenched naval guns and a series of bunkers. After a short artillery bombardment on the morning of 12 February, 2nd Battalion of the 187th attacked the north-west corner of the airfield while the 1st Battalion of the regiment and the entire 188th attacked from the south and south-eastern corners. This pincer movement succeeded in securing the airfield despite a local counter-attack, and by nightfall, the airfield was secured. The following day, the division advance across the airfield and towards Fort McKinley, the headquarters of Rear Admiral Iwabuchi, commander of the Japanese defenders on Luzon. It was during this advance that Private First Class Manuel Perez Jr.
neutralized several Japanese bunkers which were impeding the advance of the division, capturing one single-handedly and personally killing eighteen Japanese soldiers during his actions. PFC Perez was posthumously awarded the Medal of Honor for his actions. On 17 February the division launched its assault on the Fort against fierce resistance, taking heavy casualties as it drew nearer to the Fort, particularly when the Japanese detonated a quantity of naval depth charges buried under a set of lawns near the Fort. The Fort was penetrated by the 511th, however and by 18 February the area had been cleared of its defenders. On 15 February, the 1st Battalion of the 187th, alongside other American units, had also launched an attack on Mabato Point, an extremely heavily fortified position featuring the same entrenched bunkers and defensive positions seen in the Genko Line. It took six days of hard fighting against heavy Japanese resistance before the area was cleared, the airborne troops being aided by multiple airstrikes and the frequent use of napalm and heavy artillery. Sporadic resistance continued until 3 March, when all organized Japanese resistance in the area ended.
