From: Monroe, LA, USA
The Korea 50-51 scenario was the first scenario I ever played on TOAW I back in, I don't know how far back. I do remember that as a longtime board gamer just transitioning to computer games that I was amazed by what the game could do. I've played every version of the TOAW, though to be honest I haven't played much TOAW4. However, I put it on my computer from Steam this week with the idea of getting back into the game over the Christmas break. I'm a high school teacher, so I have two weeks off.
So I started Korea 50-51 and played it using basically whatever the generic rules setup is and played the first four turns. It played out pretty much like the original poster described it, but then again, pretty much like I remembered it from earlier versions of the game. Here is a very brief summary.
Turn 1. North Korea attacks and devastates the ROK defensive line at the border. The units that remain are mostly immobile. I see I have three mobile units in the south, and I move those into blocking positions along the main avenues south to slow the NK advance. I think that is a critical move for the first few turns. Put ROK units in position to slow the NK advance wherever possible. It might seem futile, but it does buy a little time.
Turn 2. North Korea continues to advance. 3 US units arrive in Pusan but are fixed in place. I have exactly ONE mobile ROK unit. I put it in position blocking the NK advance down the eastern coast toward Pusan. There are US air units in Japan, but they are fixed and not usable.
Turn 3. I have two mobile ROK units, isolated along the west coast. I use them in harassing attacks against the NK flank, in the vain hope that the AI might get distracted. It doesn't. At Pusan I now have 9 operational US units, and I set up a Pusan perimeter. One mobile ROK unit is sent up the east coast road to slow the NK advance. 4 US Air Froce units are unlocked in Japan. I have a carrier task force, but it is locked.
Turn 4. The NK forces continue to advance and push my few blocking ROK units into my Pusan perimeter or destroy them. NK and US units make contact on the east coast, but there is no NK attack. In the UN turn, I get 8 more US ground units at Pusan and 9 more ground units in Japan. The carrier task force is still locked. I stop at that point without playing the UN turn.
That is pretty much how I remember the game going in the past. The first few turns are spent mainly just sitting and watching the destruction of the ROK army while trying to slow the NK advance just a bit to allow establishment of the Pusan defensive perimeter.
The way the game played out in the past was for the UN to hold on in Pusan and then launch a flanking amphibious invasion.
So not knowing the setting used by the original poster, I think the game was pretty much working as designed. If you survive the initial NK assault, you can win decisively. You get the opportunity to launch an Inchon style amphibious along the way. But it is touch and go at first and you really have very few options the first few turns, by design.