Im aware abt the south korean troop buildup, border clashes, that the peninsula being split in the first place was due to US meddling and the fascism, mass murders and rebellions in the south but im struggling to tie it together in a way that 1) fully makes sense 2) that id be able to explain to a normie without sounding like 
Also, if u have specific articles/sources abt the border clashes and general escalation from the south, id rly appreciate that 
korea was occupied by the japanese empire for the first half of the 20th century until the end of ww2. in 1945 the american government simply decided to occupy korea up to the 38th parallel, and the soviet army cooperated for reasons, halting their advance at the 38th parallel and waiting for american troops to occupy the south. truman supported the creation of a rabidly anti-communist military government that quickly began murdering labor organizers and anyone suspected of communist sympathies. this led to the jeju uprising and massacre in 1948, during which at least 30,000 people on the south korean island of jeju were murdered by south korean security forces in a series of indiscriminate civilian massacres. after decades of occupation by foreign military empires the people of korea were prepared to fight for their own liberation, and so the north "invaded" their occupied homeland in the south to expel the american army in 1950 when it was abundantly clear that the american-backed regime would never stop murdering koreans. the americans responded by bombing every building in the north, killing 20% of the population, and maintaining military occupation of the korean peninsula for the past 75 years.