In this task, you are given a question and a context passage. You have to answer the question based on the given passage.
Q: Which region that was essentially a peninsula allowed Nurhachi to cooperate and seek friendship with the Khorchins?, Context: Relocating his court from Jianzhou to Liaodong provided Nurhachi access to more resources; it also brought him in close contact with the Khorchin Mongol domains on the plains of Mongolia. Although by this time the once-united Mongol nation had long since fragmented into individual and hostile tribes, these tribes still presented a serious security threat to the Ming borders. Nurhachi's policy towards the Khorchins was to seek their friendship and cooperation against the Ming, securing his western border from a powerful potential enemy.
A:
Liaodong