The Song used a pragmatic mix of military action, frontier defenses, and diplomacy to handle relations with Khitan/Liao and later Jin. They didn’t rely on isolation or on exclusive trade; instead, they fought border skirmishes and larger campaigns to defend and sometimes regain territory, while also pursuing treaties, tribute exchanges, and negotiated truces to keep the peace when possible. This flexible approach aimed to stabilize a vulnerable northern frontier and buy time as stronger powers rose. But the balance shifted when Jin emerged and proved capable of overwhelming northern defenses; after conquering Liao and pressing into Song lands, the Song lost significant northern territories and had to retreat south, forming the Southern Song. So this combination—warfare, frontier defense, and diplomacy—best explains Song policy toward Khitan/Liao and Jin, rather than isolation, exclusive trade, or outright conquest of these states.