Throughout the ages, Cao Cao's impressive victory at Guandu, the climactic event of his life, has drawn analysis by both historical commentators and militarists hoping to imitate his success. The Song dynasty historian Sima Guang, compiler of the chronicle "Zizhi Tongjian", remarked that while Yuan Shao was generous, elegant and able, he was also obstinate, self-satisfied, and seldom heeded reasonable advice. These negative attributes were the cause of his defeat. In more recent times, both the Chinese Nationalists and Communists have picked up on this battle and made their own interpretations, in various degrees of objectivity. The Nationalists followed traditional Chinese historiography in that they judged the battle in terms of personalities, rather than the situations and the tactics involved. For example, Cao Cao was seen as capable, decisive, and far-sighted, while Yuan Shao was derided as mediocre, slow, arrogant, and unable to employ men properly. The Communist leader Mao Zedong, in his writings about strategic retreat, used the Battle of Guandu along with the Battle of Chenggao, Battle of Kunyang, Battle of Red Cliffs, Battle of Xiaoting, and Battle of Fei River to illustrate the concept. In all of these battles, he wrote, "...the contestants were unequal in strength, and the weaker one yielding a step at first, pinned down the stronger one through delayed action and defeated him." Mao's words attracted some attention to the battle, and many papers were written to analyze the Battle of Guandu in Maoist terms. The Maoist interpretation, while taking note of Yuan Shao's serious errors of judgement, advocates that the strong enemy will make fateful errors, while the weaker opponent need only to await their appearance. The Marxist interpretation portrays Yuan Shao as the representative of the great landlord-official class, and Cao Cao as of the middle and small landlord class. The battle was thus a product of class conflict in which Yuan Shao's fall was inevitable. The historian Carl Leban attributes Cao Cao's victory to one single strategic decision — the defender's choice of location. Leban asserts that Cao Cao chose Guandu as the place to make his stand because of his superior understanding of the relation between topography, logistics, and tactics over Yuan Shao. It was the issue about logistics that prompted Cao Cao to abandon the defence at the Yellow River. By luring Yuan Shao far south into Guandu, Cao Cao had forcibly extended Yuan Shao's supply lines and was thus able to pounce on his logistical disadvantage to gain a decisive victory.