i think YOU should read on the korean war. although you did have some facts right, you only tell a small portion of the story

after the korean peninsula was split up (south to USA, north to soviet)
americans did not train and equip SK army at all. they had no intentions of unifying korea because it served as a good buffer zone to separate japan (and rest of asia) from the communist russia and china. just like how germany was split up to act as a buffer zone to block the eastern communist coutries.

whereas stalin had different intentions. as soon as he put kim il-sung in power, stalin and mao gave shit load of ships, tanks, guns, fighter planes to NK and trained troops for the eventual attack and forceful take over of SK.

that's why NK was able to easily outrun SK's defense like a piece of cake.

it's like a NFL football team against a middle school team. do you really think the middle schoolers stand a chance?

that's why they were able to occupy 90% of the korean peninsula in less than 4 months.

and guess what else happened? UN stepped in (mostly US army but lots of international forces) and drove them all the way back up to the chinese border.

and mao got pissed off that there were non communist power so close to the border that he ordered 1 million soldiers equipped with gongs and whistles to drive UN forces back down to where the 38th parallel now lies