Its okay.
Anyways, the Khitai are still in there height of power in 1000 until 1031 by the death of the Emperor Shengzong, who was the ruler at the Khitai's height. There was a treay he made against the Song when he defeated them by conquering all the way outside of Kaifeng. The treaty as called was Chanyuan, it basically established cordial relations with the Song and finalized the borders between the two. However it also was very humiliating to the Song since they had to give them tons of tributary to the Khitai. I think this part may have been the nail in the coffin of the Song to defeat the Khitai by allying with the Jurchen. If I can find a way of a POD to prevent this, I think the Khitai can survive and maintain good relations with the Song and not have them ally with Goryeo or Jurchens.
I know about the treaty, but you'll have to come up with specifics before asking any further questions. The Khitan can't be weak enough before 1000 for the Song and/or Goryeo to make inroads, but having them expand further south would cause further problems, as they would almost certainly face a two-front war with the Song and Goryeo.
Now onto Goryeo. The Khitai faced a huge defeat in 1018 in a battle with Goryeo in the Third War between the two. However by 1019 they had already assembled another large army to march on the Goryeo and
at this point both sides realized that they could not defeat each other militarily and made peace until the end of the Liao Dynasty. I can have the Khitai protect there territory at the Yalu from stopping Goryeo from encroaching them, but this needs work from what you said.
I think basically what brought the downfall of the Khitai were the Jurchens. To branch them from destroying the Khitai is to have them be absorbed into the Khitai. This can probably work, but some Jurchens will still refuse and possibly revolt still.
The Liao Dynasty after Shengzong declined and when the Jurchen revolted, the Liao were weak and couldnt stop the threat.
Maybe durng the revolt, the Liao get themselves together to some miltiary commander and defeat the Jurchen and succeed in absorbing the Jurchens after there victory and probably starting a new Khitai dynasty. This doesnt stop the intentions from the Song and even Goryeo, so this needs some tweaking
Thank you for considering, I think we should talk more on the PM
In terms of Goryeo, it adapted a hostile stance towards the Khitan because it had overrun Balhae, and when the Liao sent 50 camels in order to establish friendly relations, Taejo of Goryeo actually starved them to death. As a result, if the Liao began to show any signs of weakness, it is possible that Goryeo would attempt to push north in order to "restore" former Balhae and Goguryeo territory. IOTL, although Khitan control was strong in Liaodong, it generally left the tribes in southern Manchuria alone, which eventually led the Jurchen to conquer the Khitan after establishing friendly relations with Goryeo.
You are certainly welcome to PM me, although you should probably do more research in order to ask me more specific questions.
I think its fate that we keep meeting like this.
I think you're putting too much faith in Goryeo's ability to expand, something that historically it didn't have or didn't readily act on. Typically speaking the country was simply the successor to Unified Silla and didn't even expand outside OTL's borders for North Korea. It resisted campaigns against it, and once even established advanced border forts, but it showed no real capacity to expand very far. Liaodong may be the closest significant portion of China, but the mere act of controlling it would require the country to nearly grow an extra 50% at a minimum and would suffer the strain of controlling such a populous. As well as the strain of invading that far. The same geographical features that help protect it when being invaded hinder it from expanding far outside of the country.
Not only that, but Goryeo didn't engage in full scale campaigns against the Jurchens. Actually, they were more than content with the tribute they received from them and, as far as I'm aware, never tried to conquer them. It is one thing to muse on possible hypotheticals, but I think you're going a bit beyond that. Rather, it appears as though you believe that this was a very real, even likely possibility. Color me unconvinced.
I don't think it's fate at all, as for almost a year, I have been the only one in this entire forum who has discussed matters in detail concerning Korean history from prehistoric times to the present, and you're one of very few who is able to thoroughly discuss matters concerning East Asia in general. This also makes it very difficult for me, as I have to come up with countless scenarios by myself by relying on primary/secondary sources in Korean, limited in scope, that other people generally can't consult, and people know much more about China and Japan than about Korea due to the relative lack of sources concerning the latter.
Anyway, Goryeo temporarily expanded into a very small portion of southeastern Manchuria, and later took control of Liaodong for about a decade or so. That being said, it never managed to retain either area for long. However, expanding into areas north of the Yalu and the Tumen Rivers would require not only soldiers to migrate north and establish fortifications, but also for farmers to head north in order to produce agricultural products for the long run. In other words, although a significant amount of resources would be spent on maintaining a stable force along the border for several decades, the individual areas would eventually become self-sufficient within 50-100 years or so. Also, the expansion would be gradual, not sudden, so starting around 1050 or so, it would probably take about 50-75 years to control significant amounts of eastern Manchuria, then another 50-100 or so to take over Liaodong once the Khitan begin to fall apart. In terms of the population figures, Goryeo probably had around 8-10 million after Balhae refugees streamed in from the north, and only about 1-3 million would be able to gradually establish themselves in the northern regions after about 100-150 years or so.
Also, the reason for Goryeo's possible ability to conduct these actions is precisely that the Jurchen probably won't be a coherent entity, which would make it very difficult for the Khitan to retain its holdings in Manchuria once it starts disintegrating. There is also no particular reason for Goryeo to not ally with the Song if the former controls portions of southern Manchuria, and seeks to take over Liaodong, and China wants to push the Khitan further north and/or west.
Bump, Im being serious, I really need help
Patience. There are only a handful of people on this forum who are able to discuss affairs in detail concerning East Asia during the time period that you specified, and as for the other regions covered, I think you would have to be much more specific in order to receive any substantial responses.
If I were you, I would try to do more research in order to understand more about the regions and time periods you are covering, which covers a substantial amount, then try to ask more specific questions, as general/vague questions will only result in general/vague answers.