The corps was assigned to the Sixth United States Army in preparation for the offensive in the Philippines from the assets of the Philippine Commonwealth Army, Philippine Constabulary and the recognized guerrilla units. On 9 January 1945, I Corps successfully landed on the coast of the Lingayen Gulf in Northern Luzon with the mission of establishing a base for future operations to the north and of denying the enemy northern access to the South China Sea. As a part of the Sixth Army with an overall force of 175,000 men, the American forces faced over 260,000 Japanese in Luzon. In a sustained drive of thirty-four days which covered over 100 miles, I Corps crossed central Luzon and thus separated the Japanese forces in the north from those in southern Luzon, destroying Japanese armored units along the way. Additional landings at Samar and Palawan were conducted in February, reducing the pressure on the forces of I Corps. Following this accomplishment, the corps turned northward and began the systematic reduction of the enemy positions on the approach to the Cagayan Valley. The breakthrough into the valley was followed by a swift exploitation that took the corps to the north coast. This advance covered two hundred miles in little over 100 days; eliminating effective enemy resistance in northern Luzon. Manila was recaptured by the Allies after heavy fighting that ravaged the city. The intense fighting that ensued cost 8,000 killed and 30,000 wounded in the Sixth Army, compared to 190,000 dead for Japan. As the Sixth Army finished off the Japanese on Luzon, the Eighth United States Army in the south sent units all throughout the Philippines to eliminate remaining Japanese resistance on the islands. The Tenth United States Army in the north commenced securing Okinawa and Iwo Jima. With the defeat of the Japanese at each of these places, the US forces had locations from which to launch attacks into mainland Japan.