[3] Ma Wen did not carry a high office, having served only as high as a supply officer for one of the imperial guard corps, but Ma Jilong had passed a special imperial examination for the military strategy works of Sun Tzu and Wu Qi and later served as a prefectural prefect and military commander at You Prefecture (幽州, in modern Beijing).
When Ma Sui himself was young, on one occasion, when he was studying with his older brothers, he stated, "There will surely be disturbances in the realm.
After Ma hid there for a month, he left and joined the Tang resistance army at Pingyuan (平原, roughly modern Dezhou, Shandong) under Yan Zhenqing.
After Pingyuan fell to Yan troops, Ma fled to Wei Commandery (魏郡, in modern Handan, Hebei).
[2][4] During the Baoyin era (762–763) of Emperor Xuanzong's grandson Emperor Daizong, near the end of the Anshi Rebellion, Li Baoyu, the military governor (jiedushi) of Zelu Circuit (澤潞, headquartered in modern Changzhi, Shanxi), made Mao Sui the sheriff of Zhaocheng County (趙城, in modern Linfen, Shanxi).
When they were set to pass through Zelu Circuit, Li Baoyu could find no subordinates willing to be in charge of welcoming the Huige troops.
Ma then further warned Li Baoyu that he believed the major general Pugu Huai'en, who had accepted the surrenders of four major Yan generals at the end of the Anshi Rebellion (Li Huaixian, Xue Song, Li Baochen, and Tian Chengsi) and had recommended that they be allowed to remain as military governors, and who was also Yaoluoge Yidijian's father-in-law, might be intending to rebel and having designs on Zelu and Hedong (河東, headquartered in modern Taiyuan, Shanxi) Circuits.
On an occasion when Li Baoyu went to the capital Chang'an to pay respect to Emperor Daizong, Ma accompanied him, and Emperor Daizong, believing that Ma was able, made him the prefect of Shang Prefecture (商州, in modern Shangluo, Shaanxi) and put him in charge of the supply lines going through Shang Prefecture.
[2] In 775, the soldiers stationed at the important base Heyang (河陽, in modern Jiaozuo, Henan) mutinied and expelled their commander Chang Xiuming (常休明).
Li Lingyao launched a surprise attack against their forces and causing them to withdraw; a large portion of Li Zhongchen's army, from Huaixi Circuit (淮西, headquartered in modern Zhumadian, Henan), deserted, while the people of Zheng Prefecture panicked and fled to the eastern capital Luoyang.
Li Zhongchen wanted to retreat, but Ma opposed, stating, "We are regular troops attacking rebels.
Shortly thereafter, Ma Sui was made the acting military governor of Hedong Circuit and the mayor of Taiyuan Municipality.
Hedong Circuit had recently (in 778) suffered a major defeat against Huige forces,[6] and its army was weak at the time.
In 781, he was at Chang'an to pay homage to Emperor Dezong, when he warned Emperor Dezong that Tian Yue, who had succeeded Tian Chengsi as the military governor of Weibo Circuit (魏博, headquartered in modern Handan) in 779 and taken a conciliatory and submissive posture toward the imperial government, would nevertheless rebel eventually and that precautions needed to be taken.
Li Huaiguang also arrived and, against Ma's advice of waiting until his soldiers had enough rest, decided to battle Zhu and Wang immediately.
He had initial successes, but Wang cut his soldiers off from each other with a charge, leading to a major defeat for the imperial forces.
[8] In fall 783, soldiers from Jingyuan Circuit (涇原, headquartered in modern Pingliang, Gansu), in Chang'an to await deployment to the east, mutinied when they became angry that Emperor Dezong was not giving them rewards.
He also sent his subordinate Wang Quan (王權) with 5,000 soldiers, along with his own son Ma Hui (馬彙), to try to aid Emperor Dezong.
Emperor Dezong gave Ma Sui the title of acting Situ (司徒, one of the Three Excellencies) and created him the Prince of Beiping.
[2][9][10][11] Soon, though, with many of Li Huaiguang's subordinates turning against him, he withdrew from the Chang'an region to Hezhong (河中, in modern Yuncheng, Shanxi).
[11] He subsequently put Ma Sui in charge of the operations against Li Huaiguang, along with Hun Jian and Luo Yuanguang (駱元光).
[12] He subsequently persuaded Li Huaiguang's officer Xu Tingguang (徐庭光), who was defending Changchun Palace (長春宮, in modern Weinan, Shaanxi), to surrender, and then approached Hezhong with Hun and Luo.
Li Huaiguang, facing defeat, committed suicide, ending his rebellion, 27 days after Ma had requested one more month to subdue him.
Emperor Dezong gave Ma the additional title of Shizhong (侍中), the head of the examination bureau of government (門下省), a post considered one for a chancellor.
With Ma and another chancellor who was also a political enemy of Li Sheng's, Zhang Yanshang, advocating peace, Emperor Dezong removed Li Sheng from his command at Fengxiang (鳳翔, in modern Baoji, Shaanxi) and recalled him to Chang'an, getting ready to make peace with Tufan.
As a result of this debacle, Zhang claimed an illness and retired, while Emperor Dezong recalled Ma Sui to the capital and stripped him of his command, keeping him at Chang'an to serve as Shizhong and Situ.
[13] Later, when Li Mi advocated an alliance with Huige against Tufan, despite Emperor Dezong's longstanding hatred toward Huige—as, during an incident in 762 while he was still the Prince of Yong under Emperor Dezong, a number of his staff members had been arrested and killed by Huige's then-khan Dengli Khan Yaoluoge Yidijian (藥羅葛移地建) over a dispute in the meeting protocol between the young prince and the khan—Li Sheng and Ma spoke in favor of the alliance, finally persuading Emperor Dezong in conjunction with Li Mi's advice.
But he had the ability to capture Tian Yue and failed to do so, and he accepted the false words of the Tufan general and requested peace.