Sorry to burst your bubble, but you recall incorrectly. The 82nd did not participate in the Korean War. If you'd like to know your grandfather's specific military history, you can request his service record from the National Archives. Records are open to the public 62 years after separation from the service, so records from 1954 and earlier are public record. Otherwise, you need to be the veteran, or their next of kin. So if your grandfather was in the army beyond 1954, have his kid (your parent) make the request and you can get them.

As far as a "turning point," the 38th parallel was created much earlier, in 1945 and in 1905. The Japanese and Russians discussed the 38th parallel as the dividing line between Russian and Japanese influence in Korea during the Treaty of Portsmouth. In 1945, Dean Rusk (future Secretary of State) and Charles Bonesteel (future General and commander of Eighth US Army - US Forces Korea/UN Command) picked the line as the dividing line between Soviet and American forces for occupation of Korea, which the Soviets accepted.

Between the start of the war on June 25th 1950, and the armistice on July 27th, 1953, almost the entire peninsula had been captured by both sides, but in the end, the only major changes were the loss of Kaesong and the surrounding Ongjin peninsula to the North, and the capture of portions of Paju and Pocheon City, and Yeoncheon, Cheorwon, Inje, Hwacheon, and Yangyang County, as well as Sokcho, Goseong, and Yanggu City. Territorially, the South got more land, but they lost the historical capital of Kaeseong. Instead of having a flat line across the 38th parallel, it's a diagonal line going from about 37.7 to 38.8 west to east.

During the war itself, the major actions were:

• the start of the war on June 25th, 1950. A blitzkrieg like attack on an under-armed, under-trained, unsuspecting adversary, the DPRK's military was made up of a core of battle-hardened volunteer Koreans who had fought in the Chinese civil war. They overran the entire country up to the Naktong River and the Pusan Perimeter in about 6 weeks. Considering how mountainous the country is and how poor the roads were (even today, they can be pretty shitty, going in long, roundabout directions to avoid mountains and to follow the contour of the land), it was pretty impressive. This map shows the tiny foothold that was left.

• The height of the battle of the Pusan Perimeter began on the 4th and 5th of September with General Walker's command post evacuating Daegu for Pusan, but by the 6th, the line had stabilized. Operation Chromite, the invasion of Incheon began on September 15th and by that time, the North Korean pressure on Pusan collapsed as they began to retreat north.

• North Korean troops were north of the 38th by October 1st.

• MacArthur and the UN crossed the parallel on October 7th, and by the end of October, they had captured Pyongyang and pushed north towards the Yalu.

• Reports of Chinese soldiers in Korea began coming in during late October and on November 1st, the Chinese and American armies fought directly for the first time during the battle of Unsan.

• The Chinese spent the winter of 1950-51 expelling the UN forces from North Korea. The Battle of Chosin Reservoir and the evacuation of Hungnam occurred in November and December of 1950.

• After Seoul fell to the Communists again just after New Years 1951, the UN forces were pushed south to around the 37th parallel.

• Lt. General Matthew Ridgeway took over Eighth US Army in December of 1950 and in January-April, he led a series of brutal and aptly named operations - Roundup, Ripper, Killer, Courageous, and Tomahawk, and established lines of defense, Wyoming, Missouri, Kansas, and Jamestown. By the fall of 1951, the front had stabilized and the war was, for the most part, over. Battles continued along the lines for two more years, but no more major changes of land occurred.

That's it in a nutshell.