Sun Tzu on the Art of War: Introduction - The Commentators
Sun Tzu can boast an exceptionally long distinguished roll of commentators, which would do honor to any classic. Ou-yang Hsiu remarks on this fact, though he wrote before the tale was complete, and rather ingeniously explains it by saying that the artifices of war, being inexhaustible, must therefore be susceptible of treatment in a great variety of ways.
TS`AO TS`AO or Ts`ao Kung, afterwards known as Wei Wu Ti [A.D. 155-220]. There is hardly any room for doubt that the earliest commentary on Sun Tzu actually came from the pen of this extraordinary man, whose biography in the SAN KUO CHIH reads like a romance. One of the greatest military geniuses that the world has seen, and Napoleonic in the scale of his operations, he was especially famed for the marvelous rapidity of his marches, which has found expression in the line "Talk of Ts`ao Ts`ao, and Ts`ao Ts`ao will appear." Ou-yang Hsiu says of him that he was a great captain who "measured his strength against Tung Cho, Lu Pu and the two Yuan, father and son, and vanquished them all; whereupon he divided the Empire of Han with Wu and Shu, and made himself king. It is recorded that whenever a council of war was held by Wei on the eve of a far-reaching campaign, he had all his calculations ready; those generals who made use of them did not lose one battle in ten; those who ran counter to them in any particular saw their armies incontinently beaten and put to flight." Ts`ao Kung's notes on Sun Tzu, models of austere brevity, are so thoroughly characteristic of the stern commander known to history, that it is hard indeed to conceive of them as the work of a mere LITTERATEUR. Sometimes, indeed, owing to extreme compression, they are scarcely intelligible and stand no less in need of a commentary than the text itself. 
MENG SHIH. The commentary which has come down to us under this name is comparatively meager, and nothing about the author is known. Even his personal name has not been recorded. Chi T`ien-pao's edition places him after Chia Lin,and Ch`ao Kung- wu also assigns him to the T`ang dynasty,  but this is a mistake. In Sun Hsing-yen's preface, he appears as Meng Shih of the Liang dynasty [502-557]. Others would identify him with Meng K`ang of the 3rd century. He is named in one work as the last of the "Five Commentators," the others being Wei Wu Ti, Tu Mu, Ch`en Hao and Chia Lin.
LI CH`UAN of the 8th century was a well-known writer on military tactics. One of his works has been in constant use down to the present day. The T`UNG CHIH mentions "Lives of famous generals from the Chou to the T`ang dynasty" as written by him.  According to Ch`ao Kung-wu and the T`IEN-I-KO catalogue, he followed a variant of the text of Sun Tzu which differs considerably from those now extant. His notes are mostly short and to the point, and he frequently illustrates his remarks by anecdotes from Chinese history.
TU YU (died 812) did not publish a separate commentary on Sun Tzu, his notes being taken from the T`UNG TIEN, the encyclopedic treatise on the Constitution which was his life- work. They are largely repetitions of Ts`ao Kung and Meng Shih, besides which it is believed that he drew on the ancient commentaries of Wang Ling and others. Owing to the peculiar arrangement of T`UNG TIEN, he has to explain each passage on its merits, apart from the context, and sometimes his own explanation does not agree with that of Ts`ao Kung, whom he always quotes first. Though not strictly to be reckoned as one of the "Ten Commentators," he was added to their number by Chi T`ien-pao, being wrongly placed after his grandson Tu Mu.
TU MU (803-852) is perhaps the best known as a poet - a bright star even in the glorious galaxy of the T`ang period. We learn from Ch`ao Kung-wu that although he had no practical experience of war, he was extremely fond of discussing the subject, and was moreover well read in the military history of the CH`UN CH`IU and CHAN KUO eras. His notes, therefore, are well worth attention. They are very copious, and replete with historical parallels. The gist of Sun Tzu's work is thus summarized by him: "Practice benevolence and justice, but on the other hand make full use of artifice and measures of expediency." He further declared that all the military triumphs and disasters of the thousand years which had elapsed since Sun Tzu's death would, upon examination, be found to uphold and corroborate, in every particular, the maxims contained in his book. Tu Mu's somewhat spiteful charge against Ts`ao Kung has already been considered elsewhere.
CH`EN HAO appears to have been a contemporary of Tu Mu. Ch`ao Kung-wu says that he was impelled to write a new commentary on Sun Tzu because Ts`ao Kung's on the one hand was too obscure and subtle, and that of Tu Mu on the other too long-winded and diffuse. Ou-yang Hsiu, writing in the middle of the 11th century, calls Ts`ao Kung, Tu Mu and Ch`en Hao the three chief commentators on Sun Tzu, and observes that Ch`en Hao is continually attacking Tu Mu's shortcomings. His commentary, though not lacking in merit, must rank below those of his predecessors.
CHIA LIN is known to have lived under the T`ang dynasty, for his commentary on Sun Tzu is mentioned in the T`ang Shu and was afterwards republished by Chi Hsieh of the same dynasty together with those of Meng Shih and Tu Yu. It is of somewhat scanty texture, and in point of quality, too, perhaps the least valuable of the eleven.
MEI YAO-CH`EN (1002-1060), commonly known by his "style" as Mei Sheng-yu, was, like Tu Mu, a poet of distinction. His commentary was published with a laudatory preface by the great Ou-yang Hsiu, from which we may cull the following: -
Later scholars have misread Sun Tzu, distorting his words and trying to make them square with their own one-sided views. Thus, though commentators have not been lacking, only a few have proved equal to the task. My friend Sheng-yu has not fallen into this mistake. In attempting to provide a critical commentary for Sun Tzu's work, he does not lose sight of the fact that these sayings were intended for states engaged in internecine warfare; that the author is not concerned with the military conditions prevailing under the sovereigns of the three ancient dynasties,  nor with the nine punitive measures prescribed to the Minister of War.  Again, Sun Wu loved brevity of diction, but his meaning is always deep. Whether the subject be marching an army, or handling soldiers, or estimating the enemy, or controlling the forces of victory, it is always systematically treated; the sayings are bound together in strict logical sequence, though this has been obscured by commentators who have probably failed to grasp their meaning. In his own commentary, Mei Sheng-yu has brushed aside all the obstinate prejudices of these critics, and has tried to bring out the true meaning of Sun Tzu himself. In this way, the clouds of confusion have been dispersed and the sayings made clear. I am convinced that the present work deserves to be handed down side by side with the three great commentaries; and for a great deal that they find in the sayings, coming generations will have constant reason to thank my friend Sheng-yu.
Making some allowance for the exuberance of friendship, I am inclined to endorse this favorable judgment, and would certainly place him above Ch`en Hao in order of merit.
WANG HSI, also of the Sung dynasty, is decidedly original in some of his interpretations, but much less judicious than Mei Yao-ch`en, and on the whole not a very trustworthy guide. He is fond of comparing his own commentary with that of Ts`ao Kung, but the comparison is not often flattering to him. We learn from Ch`ao Kung-wu that Wang Hsi revised the ancient text of Sun Tzu, filling up lacunae and correcting mistakes. 
HO YEN-HSI of the Sung dynasty. The personal name of this commentator is given as above by Cheng Ch`iao in the TUNG CHIH, written about the middle of the twelfth century, but he appears simply as Ho Shih in the YU HAI, and Ma Tuan-lin quotes Ch`ao Kung-wu as saying that his personal name is unknown. There seems to be no reason to doubt Cheng Ch`iao's statement, otherwise I should have been inclined to hazard a guess and identify him with one Ho Ch`u-fei, the author of a short treatise on war, who lived in the latter part of the 11th century. Ho Shih's commentary, in the words of the T`IEN-I-KO catalogue, "contains helpful additions" here and there, but is chiefly remarkable for the copious extracts taken, in adapted form, from the dynastic histories and other sources.
CHANG YU. The list closes with a commentator of no great originality perhaps, but gifted with admirable powers of lucid exposition. His commentator is based on that of Ts`ao Kung, whose terse sentences he contrives to expand and develop in masterly fashion. Without Chang Yu, it is safe to say that much of Ts`ao Kung's commentary would have remained cloaked in its pristine obscurity and therefore valueless. His work is not mentioned in the Sung history, the T`UNG K`AO, or the YU HAI, but it finds a niche in the T`UNG CHIH, which also names him as the author of the "Lives of Famous Generals." 
It is rather remarkable that the last-named four should all have flourished within so short a space of time. Ch`ao Kung-wu accounts for it by saying: "During the early years of the Sung dynasty the Empire enjoyed a long spell of peace, and men ceased to practice the art of war. but when [Chao] Yuan-hao's rebellion came [1038-42] and the frontier generals were defeated time after time, the Court made strenuous inquiry for men skilled in war, and military topics became the vogue amongst all the high officials. Hence it is that the commentators of Sun Tzu in our dynasty belong mainly to that period. 
Besides these eleven commentators, there are several others whose work has not come down to us. The SUI SHU mentions four, namely Wang Ling (often quoted by Tu Yu as Wang Tzu); Chang Tzu- shang; Chia Hsu of Wei;  and Shen Yu of Wu. The T`ANG SHU adds Sun Hao, and the T`UNG CHIH Hsiao Chi, while the T`U SHU mentions a Ming commentator, Huang Jun-yu. It is possible that some of these may have been merely collectors and editors of other commentaries, like Chi T`ien-pao and Chi Hsieh, mentioned above.