The Liu-Guitang-biography in German (Graefe, Nils: Liu Guitang - Einer der größten Banditen der chinesischen Republikzeit,Wiesbaden: Harrassowitz, 2008) states the following:
It's quite complicated and not easy to recapitulate a chronology of Liu Guitang's army enlistings and side-switches, because often Liu was riding on different horses the same time or did not follow orders. Enlistings for him were just a way to gain more soldiers, munition, weaponry and power. Nevertheless here follows a sort of an enlisting chronology for Liu Guitang:
--- In the late 1910's Liu was enlisted in the army of Zhang Jingyao 張敬堯 and was soldier of Zhang's 7th division in Hunan. Liu himself stated that to a journalist of the Shenbao 申報 in 1932 (Graefe cites a Shenbao-report of 1. January 1932). Zhang failed in Hunan and his troops were partly wiped out or disarmed and disbanded. Liu fled back to Shandong and joined the bandit milieu of Baodugu 抱犢崮.
--- In the early 1920's: The Zhili-Clique of Wu Peifu 吳佩孚 , who had been winner over the Anhui-Clique of Duan Qirui and the mentioned Zhang Jingyao,tried to enlist Liu and his followers. But again and in the end they were disarmed and disbanded in his home district Feixian 費縣 (source: the same Shenbao-report). Liu again joined the bandit milieu of Baodugu, especially the bandit leader Liu Qingyuan 劉清元 (under Sun Meiyao 孫美瑤). Liu allegedly even had been body guard of Sun Meiyao himself.
--- 1923: After the train robbery of Lincheng 臨城, when Sun Meiyao and his men captured foreigners and hold them for ransom on the mountain Baodugu, Sun Meiyao and followers were, as a "reward" for freeing the foreigners, enlisted as a brigade of Shandong local military of the Zhili-Clique. Liu was enlisted too. But the honour lasted shortly. Sun Meiyao was beheaded in late 1923 and the rest was disarmored or managed to flee. Liu went for banditry again and became "the" leader of south Shandong banditry, committed a lot of massacres in the mid 1920's, and became a local powerholder.
--- In the late 1920's a lot of different military leaders tried to recruit him. First the Fengtian-Clique, and so Zhang Zongchang, military governor of Shandong. Actually there had been contact between forces of Zhang Zongchang, namely troops of Chu Yupu 禇玉璞, which had officially the order to annihilate the bandits, but stealthly made business with them. The bandits gave opium, the soldiers took it, shooted bullets in the sky to deceive the people, and the soldiers gave the bandits munition. At the end, in 1927, Liu Guitang was enlisted in the rows of Xu Kun 許錕, who was the commander of the 7th Army corps of Zhang Zongchang. At the same time one important follower of Liu Guitang and his bandit group, namely Li Tanggang 李堂剛, was enlisted as brigade commander of the 13th divison of the 1. Army corps of Zhan Zongchang. And, by the way, the commander of this 13th division was Gu Zhen (!!!).
--- The end of 1927, beginning of 1928, brought the northern expedition into Shandong. So Feng Yuxiang, who competed with Chiang Kaishek for the control of Shandong, and Chiang Kaishek tried to enlist Liu Guitang and his local forces. Feng Yuxiang's follower Han Fuju 韓復榘 in Henan (20th division of Feng, later Han switched side to Chiang Kaishek) contacted Liu via a mediator. Liu just took 17000 silver dollars and 2000 bags of flour, but did not care about Han anymore.
--- 1928: This year is quite complicated for a chronology, because, Liu seemingly stayed in the area of Xuchang 許昌 in Henan as divison commander of Feng Yuxiang, whom he met personally, and at the same time stayed in south Shandong, where he was enlisted as division commander of Chiang Kaishek's general He Yingqin and as a spearhead of the northern expedition (namely "北伐先遣軍"). Perhaps he traveled back and forth and deceived both Feng and He. Liu was a poker player. Everything, which helped for his power, he would do. So it is also possible, that he still even had secret ties to Zhang Zongchang and that he waited for the end of the northern expedition battles, to jump on the horse of the winner.
--- In August 1928 he ransacked the district town of Feixian 費縣 and took garrison there, in the name of the northern expedition. End of August he pulled his troops toward the prefecture town Linyi 臨沂. The town heads payed huge fees, so Liu just passed by and took the town of Juxian 莒縣. There he took garrison until february 1929 and til Yang Hucheng's troops came. . .
--- Liu retreated to the northern depression of Shandong province and in mid 1929 was transferred by train to Henan province, where he battled for Chiang Kaishek as "commander of the 4th division" of the central army of Chiang Kaishek in the "the great war of the Chinese plain" (中原大戰) of 1930 against a warlord cooperation around Feng Yuxiang 馮玉祥, Yan Xishan 閻錫山 etc.
.... to be continued. . .
