The world was in chaos 75 years ago. January 9, 1945, marked a pivotal day for the U.S. in World War II's Pacific theater when General of the Army Douglas MacArthur, the commander of U.S. troops in the South Pacific, landed on the shores of the Philippines island of Luzon. Four U.S. Army divisions and MacArthur landed on Luzon Jan. 9 and began their push toward Manila, the capital. Ultimately, 10 U.S. divisions, including the newly created Eighth Army, and five independent regiments fought on Luzon, making it the largest campaign of the Pacific war. It involved more troops than the U.S. had used in North Africa, Italy or southern France.In early fall of 1944, MacArthur outlined to Eighth Army's commander, Lt. Gen. Robert Eichelberger, his scheme for the liberation of the Philippines and his proposed employment of the newly created Eighth Army. Eichelberger had taken command of Eighth Army in Hollandia, New Guinea on Sept. 7, 1944. According to plan, Sixth Army was to take Leyte, Philippines, establish a beachhead on Mindoro, and strike a blow against Luzon at Lingayen Gulf. Eighth Army would move up to Leyte to conduct operations to regain control of the central and southern Philippines, feint toward southern Luzon from Mindoro and support Sixth Army in Luzon by delivering two sharp blows on the Philippines west coast; one at Bataan and the other south of Manila. By January 1, 1945, Eighth Army Headquarters had moved to Leyte and assumed control of operations in the Philippines south of Luzon. Eighth Army would conduct numerous combat landings taking two-thirds of the land of the Philippines in the campaign. The island nation was a strategic point in the Pacific, but it had been under Japanese control since 1942, that's when MacArthur and about 14,000 U.S. troops were forced to retreat from Manila, the Philippine capital on Luzon, which is the country's northernmost island. MacArthur vowed to return. If the U.S. could regain control of the island chain, it would be the staging area for the final assault against Japan's home islands. It would also cut Japan off from vital resources such as food and raw materials from the East Indies and Southeast Asia.The Japanese knew its importance, too. They stationed a whopping 430,000 land troops throughout the Philippines, while imperial naval leaders were willing to commit the entire battle fleet to its defense.While the Luzon landing on Jan. 9 was a major milestone, the fight to win back the Philippines began two and a half months earlier on Oct. 20, 1944, when four Army divisions landed on the central island of Leyte. Thus began the Battle of Leyte Gulf, where Allied troops aimed to get a foothold on the Philippines to prepare for the greater goal -- taking back Luzon.During the Battle of Luzon, U.S. troops liberated thousands of Allied prisoners of war who had been in captivity since the 1942 Japanese invasion and the infamous Bataan Death March.The win in Luzon was significant for many reasons, but the key takeaway is it marked the beginning of the end for Japan, and the start of "The Amphibious Eighth" legacy.- Information for this article provided by the DOD and the former 8th Army Historical Section