When the outlying semi-Chinese states surrounding the inner conclave of orthodox Chinese states, after four centuries of fighting and intrigue for the Protectorate, or at least for preponderance, at last, during the period 400-375 B.C. became the Six Powers, all equally royal, none of them owing any real, scarcely even any nominal, allegiance to the once solitary King or Emperor, then it was that the idea began to enter the heads of the Ts'in statesmen and the rulers of at least three of the Six Royal Powers opposed to Ts'in that it would be a good thing to get rid of the old feudal vassal system root and branch. So unquestionably is this period 400-375 B.C. taken as one of the great pivot points in Chinese history, that the great historian Sz-ma Kwang begins his renowned history, the _Tsz-chi Tung-kien_, published in 1084 A.D., with the words: "In 403 B.C. the states of Han, Ngwei, and Chao were recognized as vassal ruling princes by the Emperor." Ts'in took to educating herself seriously for her great destiny, and at last, in 221 B.C., after the wars already described in Chapter XXVI., succeeded in uniting all known China under one centralized sway; rounding off the Tartars so as to make the Great Wall (rather than the Yellow River, as of old) their southern limit; conquering the remains of the "Hundred Yüeh" (the vague unknown South China which had hitherto been the special preserve of Ts'u;) and assimilating the ancient empire of Shuh (i.e. Sz Ch'wan, hitherto only vaguely known to orthodox China at all, and politically connected only with Ts'in).