The first set of terminologies that manifest the vassalage perception of Koguryo during 5th century A.D. is '太王' ('greatest king') and '奴客'. The term '太王' (or simply '王' as the abbreviated form) was monopolized by Koguryo court to be used solely upon its king in the realm of its world. Later, '太王' and '王' were separated so that '太王' should strictly be representing none other than the Koguryo monarch himself, whereas '王' came to signify the lesser rulers.
In the stele monument of king Kwanggaeto, '奴客' is referred to those rulers who came under Koguryo's umbrella and were treated almost like the ordinary peasant of Koguryo('民'). Thus, '奴客' symbolized the status of subjugated rulers and their people to its power sphere. '歸王', '恩德' and '慕化' all have elaborated the relationships between '太王' and '奴客' to beautify the holy and benevolent images of the Koguryo king. Such rhetorics were then cunningly utilized as a pretext to Koguryo's war of conquest.
To achieve the substantial understanding of the concept '屬民' ('subordinates'), we must first make the meaning of '民' and '臣民' clear. '民' basically means the 'people within Koguryo's world'. The status of '臣民' is located between '屬民' and '民', so that '屬民' is inferred to be those polities nominally subjugated to Koguryo.
The 'tribute recognition' of 5th-century Koguryo implicated certain connection with '屬民' and the range of tributary states goes beyond it. Koguryo uniformly practiced hostage system to all those obligated to pay tribute, as well as substituting Chinese-style investiture with military service. Koguryo also awarded its court dresses and other prestige goods to its tributary states.
'守天' means 'guarding Koguryo's world together', thereby defining the world order of Koguryo as universal and natural. However, this '守天 awareness' did not remain as simple idealism, but did implicate certain practical cooperations between the kingdoms of lord-vassal hierarchy. Since it was Koguryo's duty as the suzerain empire to give military aid to its vassals when they were in danger, it is only logical to say that same must have been expected in the identical situation from vassals to the centre state, which makes this '守天' notion in close relationship with the 'tribute recognition'. Therefore, '守天' ultimately realizes ideal and completion of the Koguryo-oriented world order.