Wu never attempted to conquer the whole of China, but endeavoured to consolidate its own difficult territory with a view to building up a state on a firm foundation.  In general, Wu played mainly a passive part in the incessant struggles between the three kingdoms, though it was active in diplomacy.  The Wu kingdom entered into relations with a man who in 232 had gained control of the present South Manchuria and shortly afterwards assumed the title of king.  This new ruler of “Yen”, as he called his kingdom, had determined to attack the Wei dynasty, and hoped, by putting pressure on it in association with Wu, to overrun Wei from north and south.  Wei answered this plan very effectively by recourse to diplomacy and it began by making Wu believe that Wu had reason to fear an attack from its western neighbour Shu Han.  A mission was also dispatched from Wei to negotiate with Japan.  Japan was then emerging from its stone age and introducing metals; there were countless small principalities and states, of which the state of Yamato, then ruled by a queen, was the most powerful.  Yamato had certain interests in Korea, where it already ruled a small coastal strip in the east.  Wei offered Yamato the prospect of gaining the whole of Korea if it would turn against the state of Yen in South Manchuria.  Wu, too, had turned to Japan, but the negotiations came to nothing, since Wu, as an ally of Yen, had nothing to offer.  The queen of Yamato accordingly sent a mission to Wei; she had already decided in favour of that state.  Thus Wei was able to embark on war against Yen, which it annihilated in 237.  This wrecked Wu’s diplomatic projects, and no more was heard of any ambitious plans of the kingdom of Wu.

The two southern states had a common characteristic:  both were condottiere states, not built up from their own population but conquered by generals from the north and ruled for a time by those generals and their northern troops.  Natives gradually entered these northern armies and reduced their percentage of northerners, but a gulf remained between the native population, including its gentry, and the alien military rulers.  This reduced the striking power of the southern states.

On the other hand, this period had its positive element.  For the first time there was an emperor in south China, with all the organization that implied.  A capital full of officials, eunuchs, and all the satellites of an imperial court provided incentives to economic advance, because it represented a huge market.  The peasants around it were able to increase their sales and grew prosperous.  The increased demand resulted in an increase of tillage and a thriving trade.  Soon the transport problem had to be faced, as had happened long ago in the north, and new means of transport, especially ships, were provided, and new trade routes opened which were to last far longer than the three kingdoms; on the other hand, the costs of transport involved fresh taxation burdens for the