 As the North Korean communists launched their surprise invasion of South Korea on 25 June 1950, United Nations forces began to withdraw. By early August, U.N. troops outnumbered and under heavy pressure had pulled back to establish a 120-mile defensive perimeter around the port of Busan. The problem that faced the United Nations commander was how to utilize his outnumbered forces so they could break out of the beachhead and take the offensive. Aerial reconnaissance had established that supplies and reinforcements for the enemy were being funneled along two main highways through Seoul, southeastward to the Busan perimeter. After estimating the situation and considering several possible plans of maneuver, General MacArthur decided to make an amphibious attack behind the enemy lines to protect the transportation and communication hub which centered around Seoul. With the enemy's supply line cut, the 8th Army would be able to break out of the Busan beachhead and launch a simultaneous attack from the southeast. However, before the amphibious attack could be launched at Seoul's port city, Incheon, high-level conferences were necessary. In mid-August, General J. Lawton Collins, Army Chief of Staff and Admiral Forrest P. Sherman, Chief of Naval Operations, arrived in Tokyo to confer with General MacArthur and his staff. One of their main problems was the selection of troops to take part in the invasion since the United Nations forces then engaged in Korea were sufficient only for the defense of the Busan perimeter. Perhaps an even greater problem was presented by the tidal conditions at Incheon considered among the most difficult in the world for an amphibious operation. Extensive studies were made of the area including examination of scenes such as these photographed in 1945 during the U.S. occupation. It was decided that mid-September would be the best time for an amphibious assault, but even then special tactics would be necessary. In Incheon's harbor and at Wolmi, a small island which dominated the outer harbor, there was a 35-foot tidal range leaving impassable mud flats at low tide. Assault landing craft would be able to approach the beaches only during the three hours of each high tide. Troops landing in the first waves would have to stick it out alone until the next high water. Meanwhile, it was decided that the 7th United States Infantry Division, which had been on occupation duty and undergoing training in Japan's snow-covered northern region, would constitute one major ground unit of the invasion force. The entire force would be designated the 10th Corps. Part of another major ground unit of the 10th Corps came from Camp Pendleton, California. They were members of the United States First Marine Division, which was at that time deployed in widely separated areas of the world. Other units of the division were assembled from the Mediterranean area and Hawaii. Still other First Division Marines were already in Korea, helping to throw back the all-out communist attacks on the Busan beachhead. Because of their combat experience, they were pulled out of the lines two weeks before the invasion to spearhead the attack on Incheon. While the invasion force was being assembled, B-29s and other planes of the UN Air Force were softening up the Incheon Seoul area for the assault. North Korean defense positions were destroyed, and communist supplies and reinforcements from the north cut off. Ships and aircraft of the United Nations fleet joined in softening up the Incheon area. To confuse the enemy, bombardments were directed at other coastal cities including Pohang, Kunsan, Samcheok, and Yeongdeok. By this time, the ships of Task Force 77, a United Nations armada, had left Japan with its cargo of 10th Corps troops and was nearing the west coast of Korea. Navy crews were getting ready for D-Day. Ground troops were making final preparations to hit the beach. On D-2, six UN destroyers closed in to draw fire from Wolmese and Incheon's shore batteries so they could be definitely located. 1,000 yards, 900. As soon as the shore batteries opened up, our destroyers returned fire and moved in closer. The probing action was successful. Every shore battery fired and was pinpointed for later destruction by air and naval bombardment, thus preventing many potential casualties among troop-loaded transports and landing craft. One of the destroyers, the Colette, received direct hits from a shore battery only 600 yards away. The preparations were completed and this was the invasion plan. At 0600, 15 September, after a pre-invasion bombardment, the third battalion of the 5th Marine Regiment would land at Wolmese and secure the island during the hours of the morning high tide. On the evening high tide at 1800, the remainder of the 5th Marine Regiment and the 1st Marine Regiment would simultaneously attack the city of Incheon from the north and south respectively. These two regiments, followed later by the 7th Marine Regiment, would move inland as rapidly as possible along the Incheon-Soul axis. Their primary mission was to capture the city of Seoul. As soon as possible after the 1st Marine Division was assured, the U.S. 7th Infantry Division would be landed through the port of Incheon, proceed east along the Incheon-Soul axis, then turn south toward Suwon to protect the southern flank and establish a line against which the 8th Army could crush the retreating communists. The 1st Korean Marine Regiment would clear captured areas and the 187th Airborne Regimental Combat Team would be held in reserve in Japan. On 15 September, dawn broke off the island of Wolmese. Guns of the 262 ship United Nations Armada began their point-blank preliminary bombardment. Tiny Wolmi broke into flames as naval gunfire hit enemy ammo and fuel dumps. General MacArthur observed from the command ship. At 06.30, the invasion began. 15 seconds before the Marines hit the beach, the bombardment was lifted at Wolmi, but continued at Incheon. They hit the beach on schedule, completely combat loaded. Because of the tidal conditions, men in this first wave could expect no supplies or reinforcements for 10 hours. The island was defended by about 400 soldiers of the 18th North Korean Division, but with the air and naval bombardment as well as close ground support by the 1st Marine Air Wing, only sporadic resistance was encountered. Communist troops in a state of shock surrendered after only light opposition. By the morning of 16 September, Incheon had been taken against light resistance. While the 1st Korean Marine Regiment cleared the city, the United States 1st Marine Division started toward the Han River and beyond it, the former South Korean capital of Seoul, which lay about 20 miles from the Incheon beachhead. Four miles out of Incheon, they passed burning Russian-made D-34 tanks. There was no definite enemy defense line on the road to Seoul, but small communist pockets of resistance had to be cleaned up. Elements of the 1st and 5th Marine Regiments cleared the rice paddies near the village of Akia. On 18 September, a launch neared shore between Incheon and Seoul. A board was General MacArthur. He was met by Major General Edward M. Allmond, commander of the 10th Corps. As General MacArthur came ashore, he was greeted by Major General O.P. Smith of the 1st Marine Division. On the same date, troops of the U.S. 7th Infantry Division landed at Incheon. First to disembark were men of the 32nd Regiment. They moved rapidly inland, then southward to form the base of an anvil against which the 8th Army driving north would crush the North Koreans. Major General David G. Barr, 7th Division commander, conferred with General Smith to coordinate army and marine action. On 19 September, the 5th Marine Regiment was maneuvering along the west bank of the Han River, poised to launch an amphibious attack. Red defenses were softened before the crossing was attempted. In the early morning hours of 20 September, the 5th Marine Regiment started a cross against enemy resistance. It was expected that the crossing would be difficult, for the river is very wide in this area. However, leading marine elements quickly made the crossing. They rapidly established a six-mile front on the far bank. By mid-morning, all opposition in the landing area had ceased, and remaining marine elements crossed without difficulty. They had cleared the greatest barrier between Incheon and Seoul. Now they lost no time in heading toward the former capital. Meanwhile, far to the south, the 8th Army led by Lieutenant General Walton H. Walker broke out of the Pusan perimeter as Communist troops were cut off from supplies and reinforcements by the 10th Corps. The Reds in South Korea were in full retreat, and one of the major objectives of the Incheon invasion had been achieved. In the Seoul area, Kimpo Airfield, captured by the 5th Marine Regiment on 17 September, was soon operational. A full-fledged airlift was quickly begun with about 400 tons of critically needed supplies being brought in daily. General MacArthur, arriving at the airfield after a frontline inspection tour, again conferred with his combat commanders. He discussed the tactical situation with General Almond. Held in reserve in Japan, the Air Force 187th Regimental Combat Team was landed at Kimpo on 23 September, quickly rushed to a staging area and ordered to proceed northward to capture the Kimpo Peninsula. By 23 September, Marines of the 5th Regiment were slowly advancing toward the suburbs of Seoul. When resistance in the suburbs proved extremely heavy, the Marine Commander decided to have the 1st Marine Regiment cross the Han in the vicinity of Yangdongpo east and south of where the 5th Marine Regiment had crossed, then moved them into the city through and south of the 5th Regiment's position. Fighting in Seoul suburbs now reached the house-to-house stage as the Reds fortified some of the main buildings. On 24 September, with the Marines still meeting fanatical opposition, General Almond decided to speed the plan for the capture of Seoul by utilizing elements of the 7th Infantry Division to envelop the southern portion of the city. This was the general situation of the 10th Corps on 24 September. The 187th Airborne Regiment and the Korean Marines were destroying the enemy on the Kimpo Peninsula. The 7th Marine Regiment was driving the enemy to the north. The 5th and 1st Marine Regiments fighting in the suburbs of Seoul were encountering fierce enemy resistance which precluded an early capture of the city. The 7th Infantry Division having seized the important airfield at Suwon was deployed on the southern flank. Now the commanding general 10th Corps directed the 7th Division commander to commit one of his regiments in an amphibious crossing of the Han River. The regiment's objective was to attack the city amphibiously from the south, capture South Mountain, the commanding terrain in the city, and envelop the enemy's southern flank. The 32nd Regiment, 7th Infantry Division, quickly moved to follow General Almond's new orders. At 0630 on 25 September, after a 30-minute artillery barrage the 32nd Regiment began its crossing southeast of Seoul. The infantrymen reached the far bank without serious opposition. However, a short distance from the river they ran into heavy small arms and machine gun fire. By noon the 32nd Regiment had captured South Mountain. With this commanding terrain in our hands the defenses of Seoul virtually collapsed. Marine and 7th Division units assisted by the 17th Rock Regiment drove to the south of Seoul and the 17th Rock Regiment drove the North Koreans out of the city on 26 September. On 27 September, 7th Division troops waited near Osan for a flying column of the US 1st Cavalry Division. As these 10th Corps and 8th Army soldiers linked up, thousands of Communists were trapped. The Anvil and the Hammer were joined. In the Republic of Korea's War Scout Capital on 29 September they participated in Seoul's Liberation Ceremony. To Dr. Seung-mon Ri South Korea's 75 year old President the UN Commander restored the city. With the 8th Army moving through its position the 10th Corps was relieved of all tactical responsibility on 7 October. In 22 days it had completed its job in the Seoul area and was on its way to another amphibious operation.