Xue Rengui - During Emperor Gaozong's Reign

During Emperor Gaozong's Reign

After Emperor Taizong's death in 649, his son Li Zhi succeeded him (as Emperor Gaozong), and for the first few years of Emperor Gaozong's reign, Xue Rengui appeared to remain a commanding general for the imperial guards. In 654, when Emperor Gaozong was visiting the vacation palace Wannian Palace (萬年宮, in modern Baoji, Shaanxi), there was a major storm. On the night of June 22, it rained particularly hard, and a flash flood descended on the Xuanwu Gate of Wannian Palace. The imperial guards all fled, but Xue did not, and instead climbed up the gate and yelled loudly inside the palace to warn the emperor. Emperor Gaozong quickly got out of his bed and climbed as high as he could, and in brief time, the water flooded into his bedchambers, and this flood killed some 3,000 residents of Linyou County, where the palace was located, and imperial guards. Afterwards, Emperor Gaozong made the comment to Xue, "It is only by your call that I avoided drowning, and from this I know that you are a faithful subject." He awarded Xue a horse.

In 657, when the general Su Dingfang attacked Western Tujue's Shaboluo Khan Ashina Helu (阿史那賀魯), Xue submitted a suggestion that if the wife and children of the chief of one of Western Tujue's constituent tribes, Nishu Tribe (泥孰), who did not particularly support Ashina Helu but was forced to comply after Ashina Helu took his wife and children hostage, were to be captured by Tang forces, that they be immediately released so that the chief of Nishu would submit to Tang. When Emperor Gaozong approved this suggestion, the chief of Nishu did, indeed, join Tang's army. Su was subsequently able to defeat and capture Ashina Helu.

Later that year, Xue was made deputy to the general Cheng Mingzhen (程名振) in an operation against Goguryeo, and they captured Goguryeo's city Chifeng (赤烽, in modern Fushun, Liaoning) and defeated the Goguryeo general Du Bangnu (豆方婁). In 659, Xue further defeated the Goguryeo general Wen Shamen (溫沙門). He also engaged Qidan forces, capturing their chief Abugu (阿卜固) and taking him back to the eastern capital Luoyang. For this achievement, he was created the Baron of Hedong.

In 661, after the chief of Tang's vassal Huige, Yaoluoge Porun (藥羅葛婆閏) died and was succeeded by his nephew Yaoluoge Bisudu (藥羅葛比粟毒), Yaoluoge Bisudu broke away from Tang and allied with two other tribes, Tongluo (同羅) and Pugu (僕固) in attacking Tang's northern boundary. Emperor Gaozong commissioned the general Zheng Rentai (鄭仁泰) to be in charge of an operation against Huige, while making the Xue and Liu Shenli (劉審理) Zheng's deputies. When they encountered Huige's coalition forces—which by this point appeared to include all nine major tribes of Tiele—the coalition challenged Tang forces to a small battle, with Tiele sending out their 10 fiercest warriors. Xue personally engaged them and killed three of them with three arrows, intimidating the Tiele coalition and causing them to submit—but after their surrender, he ordered to kill all the ten and several thousands people. From this incident, a military song was written to praise Xue's ferocity, including the words: "The general is able to pacify Tian Shan with three arrows, and the warriors sing their long songs as they enter the boundaries of Han." After the army returned to Tang territory, however, Xue was charged with killing those who had already surrendered and seizing the spoils of war and arrested for a time, but was eventually released after Emperor Gaozong ruled that the achievements outweighed the crimes.

In 666, Yeon Gaesomun died, and infighting developed between Yeon's oldest son Yeon Namsaeng, who succeeded Yeon Gaesomun as Dae Mangniji, and two younger sons Yeon Namgeon and Yeon Namsan, over suspicions that they had for each other. Eventually, Yeon Namgeon, while Yeon Namsaeng was away from the capital Pyongyang, claimed the Dae Mangniji title himself. Yeon Namsaeng sent his son (later known as Cheon Heonseong/Quan Xiancheng (泉獻誠), as Yeon (淵) was the same character as Emperor Gaozong's grandfather Emperor Gaozu's name Yuan and therefore could not be used as part of naming taboo) to seek aid from Tang. When Emperor Gaozong sent the generals Pang Tongshan (龐同善) and Gao Kan (高侃) to aid Yeon Namsaeng, Yeon Namgeon tried to intercept them, and Xue, who trailed them, marched forward to aid them, allowing them to defeat Goguryeo forces together. After they captured the cities of Namso (南蘇, in modern Tieling, Liaoning), Mokjeo (木底, in modern Fushun), and Changam (蒼巖, in modern Benxi, Liaoning), they were able to rendezvous with Yeon Namsaeng. In spring 668, they further marched east and captured Goguryeo's major northeastern city Buyeo (扶餘, in modern Siping, Jilin), and Xue was described to have marched to the sea (probably Sea of Japan) and taking some 40 cities in Goguryeo's northeastern territories, before marching southwest to rendezvous with the supreme commander of the entire operation, Li Ji, at Pyongyang. After Pyongyang fell later in 668, thus ending Goguryeo, Emperor Gaozong ordered that Goguryeo territory be annexed into Tang territory and that a protector general (known as the Protectorate General to Pacify the East) by established at Pyongyang, with Xue appointed as the protector general to defend Pyongyang, along with the general Liu Rengui. Emperor Gaozong created him the Duke of Pingyang. It was said that Xue was a capable administrator and was, for a while, able to receive allegiance from the people of Goguryeo.

In 670, Tufan launched a major attack on Tang's Xiyu (i.e., formerly Western Tujue) holdings, capturing 18 prefectures. Emperor Gaozong commissioned Xue to command a major counterattack, with Ashina Daozhen (阿史那道真) and Guo Daifeng (郭待封) as his deputies. However, as Guo previously was of the same rank as Xue, he viewed serving as Xue's deputy as a dishonor and often disobeyed Xue's orders. Xue's initial strategy was to take some troops ahead toward, with Guo remaining behind at Qinghai Lake with the military supplies—and once Xue had cleared the pass, he would then signal for Guo to proceed. Guo, however, disobeyed the order and did not wait for Xue's signal, but proceeded after Xue departed, and he was intercepted and defeated by a 200,000-men Tufan army. After Guos' army collapsed, Xue was himself attacked by the Tufan prime minister Lun Qinling (論欽陵) and defeated. Nearly the entire army was lost, and Xue was forced to sue for peace under unfavorable terms. Emperor Gaozong sent the official Le Yanwei to the front to put Xue, Guo, and Ashina under arrest, but released them once they were brought back to the capital Chang'an. However, they were relieved of their posts.

At later time, when the people of Goguryeo were rising in resistance to Tang occupation, Xue was put in charge of pacifying the region, but yet later, probably in 675, Xue was deposed for reasons not clearly stated in historical records and exiled to Xiang Prefecture (象州, roughly modern Laibin, Guangxi), only allowed to return from exile when a general pardon was declared. In 681, Emperor Gaozong, remembering Xue's contributions, summoned him and again made him a general. In 682, when remnants of the Eastern Tujue, rising under the chiefs Ashina Gudulu and Ashide Yuanzhen (阿史德元珍), declared independence from Tang, Xue was commissioned to attack Ashide Yuanzhen. His presence intimidated the Eastern Tujue soldiers, who had thought that he was long dead, and he scored a major victory over Ashide Yuanzhen.

Xue died in 683. His sons Xue Ne and Xue Chuyu (薛楚玉), and several later descendants would serve as generals as well.