The official imperial historiography of China had developed during the Western or Former Han Dynasty. The historians Sima Tan and his son Sima Qian had invented a style of history writing that divided the whole book into two to five different types of chapters. The first are the biographies of the emperors (benji 本紀 or simply ji 紀), strictly chronological inside the report and not only reporting enfeoffments or military campaigns, but also important metaphysical events like thunders, earthquakes, and so on. The second chapter type are the biographies of important people (liezhuan 列傳 or simply zhuan 傳), beginning with the empresses and consorts, down to the scholars, and to geographical reports about foreign countries. Except these two types, there were some biographies of noble families (shijia), chronological tables (biao), and treatises or monographies (shu or zhi). This biographical-monographical style of historiography was called jizhuanti 紀傳體 "biographical style", because the biographies are the guideline for division into chapters. To have an overview over a person's life or a special topic like penal law or tax system, this style is adequate, but it fails to depict the historical context of a whole aera.
To give a context for historical causes and results, a simple chronological style is much better. The classical book Spring and Autumn, the annals of the state of Lu during the early Eastern Zhou period, is the forerunner for this type of historiography. It is strictly chronological and lists the events of every year under the respective season or the month. This type of historiography is called biannianti 編年體 "chronological style - linking year after year".
The Song Dynasty scholar Sima Guang (1019-1086) decided to compile a universal history in this style that reached the Warring States period (409 BC) to begin of Song Dynasty (959 AD). His book should serve as a guideline for the crown prince to govern in a righteous way and to learn the faults of the past, and the wise and clever rulers. The book was given the name Zizhi tongjian 資治通鑒 "Comprehensive mirror to aid in government".
Although the biographical style of historiography was in use until the end of Qing Dynasty, the new "comprehensive mirror" type became so popular that people of the next generations and centuries wrote sequels of the great opus of Sima Guang, and even filled the time back until the year when Sima Guang let his book begin. Here the most important examples:

• Zizhi tongjian waiji 資治銅鑒外記 by Liu Shu 劉恕 (1032-1078), mythological times to the end of Spring and Autumn period
• Xu Zizhi tongjian changpian 續資治通鑒長編 by Li Tao 李燾 (1115-1184), Northern Song: 960-1126
• Jianyan yilai xinian yaolu 建炎以來繫年要錄 and Jianyan yilai chaoye zaji 建炎以來朝野雜記 by Li Xinzhuan 李心傳 (1166-1243), 1127 on (Southern Song)
• Zizhi tongjian qianbian 資治通鑒前編 by Jin Lüxiang 金履祥 (1242-1303), mythological times to the end of Spring and Autumn period
• Song Yuan Zizhi tongjian 宋元資治通鑒 by Wang Zongmu 王宗沐 (16th cent.), Song and Yuan Dynasties
• Zizhi tongjian houbian 資治通鑒後編 by Xu Qianxue 徐乾學 (Qing Dynasty), Song and Yuan Dynasties, lost
• Xu Zizhi tongjian 續資治通鑒 by Bi Yuan 畢元 (1729-1797), Song and Yuan Dynasties

The commentaries (音註 yinzhu) of Hu Sanxing 胡三省 (1230-1287) are today an integral part of the Zizhi tongjian itself and include the shiwen 釋文 commentary of Shi Zhao 史炤 (1100-1160). The Ming scholar Wang Yinglin 王應麟 (1223-1296) wrote a geographical compendium for Sima Guang's history, and a reader's digest of questions and answers about this huge universal history. There exist many other commentaries, revisions and thematical essays about the Zizhi tongjian.
See an example of the Mirror, reporting the events of the battle at the Red Cliff.

65. Records of Han 57, Emperor Han Xiandi, 13th year of the era Jian'an ("Establishing peace").
ZHUGE LIANG said: "Although our armies of Yuzhou have been defeated at Changbang, the people returning together with GUAN YU's naval army are ten thousand well equipped man, and there are not less than ten thousand soldiers who fought at Jiangxia under LIU QI. On the other side, CAO CAO's men are tired and exhausted, pursuing the Yuzhou army, their light cavalry did not have a rest for one day and one night on a distance of more than 300 miles. [...] And, the northern people are not accustomed with water ways. CAO CAO's followers in the area of Jingzhou do not serve him with their heart and feelings. Uniting the armies of mmed with carts and crowded with people, the lapels of the clothes looking like one single hem, the risen sleeves like a single curtain, working people spreading sweat like rain. The families are prosperous and wealthy, their wishes are high and spreading around. There is nobody who could match your sovereignity's wisdom and Qi's strength. To go to the West to serve Qin as a nominal vassal, would be a shame for your Majesty in my humble eyes.
「且夫韓、魏之所以畏秦者，以與秦接界也．兵出而相當，不至十日，而戰勝存亡之機決矣．韓、魏戰而勝秦，則兵半折，四境不守；戰而不勝，以亡隨其後．是故韓、魏之所以重與秦戰而輕為之臣也．
The reason why the states Hann and Wei fear the state of Qin is, because they have a common frontier with Qin. If the troops march out to meet face in face, they don't have to walk even ten days, and victory in a battle is a crucial decision for living and dying of a state. If Hann and Wei can defeat Qin in a war, it is only half a victory, because the four frontiers can not be hold. If the two states are defeated in a war, the slain soldiers will flee in the back of their rearguards. This is the reason why Hann and Wei pay more attention to the question of war with Qin and more readily would be its vassal.
「今秦攻齊則不然，倍韓、魏之地，至闈陽晉之道，徑亢父之險，車不得方軌，馬不得並行，百人守險，千人不能過也．秦雖欲深入，則狼顧，恐韓、魏之議其後也．是故恫疑虛猲，高躍而不敢進，則秦不能害齊，亦已明矣．夫不深料秦之不奈我何也，而欲西面事秦，是臣之計過也．今無臣事秦之名，而有強國之實，臣固願大王之少留計．」
Now, if Qin wants to attack Qi, the case is not the same. Qin would have to hurry across the territories of Hann and Qin, until it reaches the Road of Southern Jin and proceeds through the pass of Kangfu, where their chariots can not use the wide tracks and their horses are not able to go side by side. One houndred man are able to hold the pass, and one thousand man are not able to pass through. Although Qin desires to penetrate deep into other territories, its great fear is that Hann and Wei could argue behind its back. For this reason, Qin is full of doubt and anger, it makes great jumps but does not dare to go forward. Therefore, it is already very clear that Qin can do no harm to Qi. If no one has thought about it carefully enough to perceive that Qin can do you no harm and yet has urged you to proclaim your country vassal to the West then your minister's planning has been remiss. At the moment you are not Qin's vassal in name and you are still a powerful state in fact. I would like to beg you to keep my plan a little in your mind."
齊王曰：「寡人不敏，今主君以趙王之教詔之，敬奉社稷以從．」
The king of Qi said: "I am not very intelligent, but told me of the plans of the king of Zhao. I will pay respect and give offerings to the altars of the Earth, all follow your advice."