Emperor Huai, in contrast with the
developmentally disabled Emperor Hui, was intelligent and astute, and he sought to revive the war-ravaged empire, but Sima Yue maintained a tight grip on authority and would not allow the emperor much actual power. On 18 May 307, he left Luoyang and set up headquarters at Xuchang (, in modern
Xuchang,
Henan), but continued to control the government remotely. He also gave his younger brothers various titles and military appointments.
Sima Teng, the second brother, was appointed Prince of Xincai, and was made Chief Controller of Si and Ji Provinces, while being garrisoned at Ye.
Sima Lüe, the third brother, was made General who Attacks the South, Chief Controller of Jing Province and was garrisoned at Xiangyang.
Sima Mo, the youngest brother, was appointed Grand General who Conquers the West and Chief Controller of Qin, Yong, Liáng and Yi provinces. He was garrisoned at Chang'an. Later that year, on 25 August, at the urging of his wife Princess Pei, he issued an order that appeared insignificant at the time but would turn out to be important later on—making
Sima Rui the Prince of Langye in charge of Yang Province (, modern
Zhejiang and southern
Jiangsu and
Anhui), at the post of
Jianye (, in modern
Nanjing,
Jiangsu); this was the post from which Sima Rui would later, after the fall of Luoyang and Chang'an to
Han-Zhao, claim the Jin imperial title. Despite his suspicion of Emperor Huai, Sima Yue was still willing to keep him on the throne. He strongly rejected attempts to have the emperor replaced with the teenage
Sima Tan, Emperor Hui's nephew and initial Crown Prince after his direct male descendants had all died, perhaps intending to control an emperor with slightly more agency than the previous one. On 24 March 308, a few months after foiling a conspiracy to install Sima Tan to the throne, Sima Yue ordered the former crown prince to be killed. In 309, Sima Yue, concerned about the growing use of authority that Emperor Huai was exerting, made a sudden return to Luoyang and arrested and executed a number of Emperor Huai's associates, including Emperor Huai's uncle Wang Yan (). Other than privately mourning them, there was nothing that Emperor Huai could do. Sima Yue further disbanded the imperial guards and put his own personal forces in charge of protecting the emperor. For all of Sima Yue's assertion of authority, he could not stop Han-Zhao, under its generals
Liu Cong the Prince of Chu (the son of Han's emperor
Liu Yuan),
Liu Yao the Prince of Shi'an (Liu Yuan's nephew),
Wang Mi, and
Shi Le, from disrupting Jin rule throughout northern and central China and capturing Jin cities and towns. Sima Teng was killed by rebels in Ye, while Mo, Lüe and Rui were not as cooperative as Yue had expected them to be, being more interested in consolidating their own territories. Yue and his allies were able to defeat Han on numerous occasions, such as in late 309, when he managed to fight off a joint attack by Liu Cong and Wang on Luoyang, but their forces were gradually worn out while rebel groups in the north continued to attach themselves to the Han. After Liu Yuan died in 310 and was succeeded by Liu Cong, Han renewed its attacks on the Luoyang region. Meanwhile, Sima Yue continued to alienate other generals and officials, and when
Liu Kun, the military commander of
Bing (, roughly modern
Shanxi) proposed to him the plan of an attack on the Han capital Pingyang (, in modern
Linfen,
Shanxi) in conjunction with the powerful
Xianbei chieftain
Tuoba Yilu the Duke of
Dai, Sima Yue was fearful of backstabbing attack by some of these warlords and therefore unable to accept Liu's plan. Indeed, when Emperor Huai and Sima Yue sent out calls for the various governors to come to Luoyang's aid later that year, there were few responses. Sima Yue became uncertain of himself, and late in 310 left Luoyang with virtually all of the central government's remaining troops, along with a large number of officials, effectively stripping Luoyang and Emperor Huai bare of their defenses, except for a small detachment commanded by Sima Yue's subordinate He Lun (), intended as much to monitor as to protect Emperor Huai. From that point on, Luoyang was left even without a police force and became largely a city abandoned to bandits and thugs. Emperor Huai soon entered into a plan with
Gou Xi, the military commander of Qing Province (, modern central and eastern
Shandong), who had been dissatisfied with Sima Yue, to overthrow Sima Yue's yoke. Sima Yue discovered this plan, but was unable to wage a campaign against Gou. He grew ill in his anger and distress, and died in April 311. ==Postmortem developments==