There was expectation that Li Mi would prevail over Sui forces and establish a new dynasty—so much so that even other key rebel leaders, including Dou Jiande, Meng Haigong (孟海公), Xu Yuanlang, and Zhu Can, were urging him to take imperial title.
Even Li Yuan (soon to become the founder of the Tang dynasty as Emperor Gaozu) was writing him in supplicating terms that implicitly supported his imperial claim.
By the time of his father Li Kuan (李寬), who carried the Sui-created title of Duke of Pushan, the clan, although not originally from there, lived at the Sui capital Chang'an.
Due to his father's position, Li Mi became a guard of Emperor Yang of Sui, and he was said to view money lightly, using it to instead gather friends around him.
Li made the comment to his relatives, "The Duke of Chu wanted to rebel, but does not know how to gain final victory.
Further, the forward forces returning from the Goguryeo front, under the command of Qutu Tong (屈突通) and Yuwen Shu, soon arrived as well, and while Yang Xuangan attempted to prevent them from crossing the Yellow River, attacks from Fan prevented Yang Xuangan from being able to cut Qutu and Yuwen off at the Yellow River, allowing them to cross.
In anger, Yang Xuangan put Hongnong under siege, despite Li Mi's pleas that he was endangering his campaign by proceeding slowly.
They showed their jailers their gold, and told them, "When we die, please spend the proceeds to bury us; the rest of it, we leave it as a gift."
When they reached Wei Commandery (魏郡), they got the jailers drunk, and then Li, Wang, and five others dug a hole on the wall and escaped.
For the next few years, Li travelled around, trying to find an agrarian rebel leader who would listen to his grand strategies, but his attempt to persuade Hao Xiaode (郝孝德) and Wang Bo (王薄) fell on deaf ears.
At one point, he took the pseudonym Liu Zhiyuan and began teaching students in farming communities in Huaiyang Commandery (淮陽, roughly modern Zhoukou, Henan) how to read and write.
He then went to his brother-in-law, Qiu Junming (丘君明), who was then the county magistrate for Yongqiu (雍丘, in modern Kaifeng, Henan).
Li therefore suggested to Zhai that, with Emperor Yang away at Jiangdu (江都, in modern Yangzhou, Jiangsu), he should gather his troops and attack Sui's two capitals: Luoyang and Chang'an.
In response, Emperor Yang sent the general Zhang Xutuo (張須陀), who had previously been successful against rebel leaders, to attack Zhai.
Zhang was initially able to fight his way out of the encirclement, but as he tried to rescue some of his officers, he was killed in battle, and Zhai's reputation was greatly enhanced, and he was able to gather much food supply.
The Sui generals Liu Changgong (劉長恭) and Fang Shi (房崱), viewing Zhai's forces as nothing more than bandits looking for food, took them lightly and attacked.
As a result, more than 200,000 men joined Li Mi within about 10 days, and a number of commanderies submitted to him, including the major rebel generals Dou Jiande and Zhu Can.
The hermit Xu Hongke (徐洪客), however, pointed out to him that once the food supplies ran out, he would have lost his opportunity, and therefore suggested making an attack along the Grand Canal against Jiangdu (江都, in modern Yangzhou, Jiangsu), where Emperor Yang was at, arguing that capturing Emperor Yang would cause the entire empire to submit to him.
Li initially hesitated, believing that this would cause disunity among the ranks, but Zheng finally persuaded him that Zhai was too much of a risk.
A larger threat loomed for Li Mi, however, as late in spring 618, a coup led by Yuwen Huaji (Yuwen Shu's son) at Jiangdu killed Emperor Yang, and Yuwen Huaji, after declaring Emperor Yang's nephew Yang Hao emperor, began to lead the elite Xiaoguo Army (驍果) back north, toward Luoyang, posing a major threat to Li Mi's hold over the region.
At Chang'an, Li Yuan had Yang You pass the throne to him, establishing Tang dynasty as its Emperor Gaozu, while at Luoyang, the Sui officials, led by a collective leadership of Duan Da, Wang Shichong, Yuan Wendu (元文都), Huangfu Wuyi (皇甫無逸), Lu Chu (盧楚), Guo Wenyi (郭文懿), and Zhao Changwen (趙長文), declared Yang Tong emperor.
Upon hearing of Yuan and Lu's deaths, Li broke off the peaceful relations with Yang Tong's regime, now under Wang's control.
In addition, his supply of new adherents began to dry up when he, in an ill-advised decision pushed by his secretary Bing Yuanzhen (邴元真), who could materially benefit from the transactions, to trade food with Wang for textiles.
In addition, his troops were tired, and a substantial percentage of his men were injured from fighting the elite Xiaoguo Army under Yuwen's command.
However, his generals Chen Zhilüe (陳智略), Fan Wenchao (樊文超), and Shan Xiongxin all advocated a head-on engagement against Wang, and Li accepted their suggestion.
He discussed the situation with Wang Bodang, who had followed him to Chang'an, and they believed that, with Xu Shiji and Zhang Shanxiang (張善相) still having substantial troops under their control, that he could reestablish himself.
Li Mi thus spoke with Emperor Gaozu and offered to head back east to persuade his old adherents to submit to Tang.
Around the new year 619, Emperor Gaozu, despite opposition by many of his officials, agreed, and he sent Li Mi east, assisted by Jia Runfu (賈閏甫) and Wang Bodang.
Li Mi had reached Chousang (綢桑, in modern Sanmenxia, Henan) by that point, and he was fearful of what Emperor Gaozu was intending.
Traditional Chinese historians, while writing from a Tang perspective, nevertheless could not help to show admiration for Li Mi and some degree of lament.