Konstantin Petrovich Nechaev

Nechaev accepted, and recruited about 150 White Russians as mercenaries for Zhang's army, organizing them into two companies and leading them to Shanhaiguan District[23] in August 1924.[24][4] Mercenary service was attractive for White émigrés due to the fact that many of them had problems finding stable employment, and the warlords at least offered a regular income.[25] Nechaev was popular among his troops,[12] and his unit was quickly expanded, counting about 700 White Russians by the start of the Second Zhili–Fengtian War. In this conflict against Wu Peifu's Zhili clique, the Russians fought as part of the Fengtian foreign legion which also included 300 Japanese mercenaries and two Chinese companies. Nechaev commanded both the White Russians as well as the Chinese, while the Japanese operated under their own leaders.[24][26] The foreign legion also included several armoured trains that the White Russians had brought with them from Russia.[4][17][27] Nechaev and his troops fought as part of General Jin's First Army during the Second Zhili–Fengtian War. In course of these operations, Nechaev and several other White Russian mercenaries were featured in the propaganda film Modern Warfare in China 1924–1925 which was produced by the Soviet Union.[28] As the Soviet government was opportunistically supporting the anti-Left Fengtian clique at the time,[29] the White Russian general and his fellow anti-communist soldiers were portrayed favorably and sympathetically by the film's director, a Red Army colonel named Grinevskii.[29] The "honeymoon between Zhang and the Soviets (...) was brief in the extreme", however, and had already ended by mid-1925.[30] The Soviet government instead increased its support for forces opposed to Zhang, such as warlord Feng Yuxiang and the Kuomintang in southern China.[31]

Zhang Zongchang, the warlord who served as Nechaev's direct superior for much of his mercenary career

Following the Fengtian clique's victory over the Zhili forces in November 1924, Nechaev led his mercenary force to Jinan, where he was placed under the command of Zhang Zongchang, the ruler of Shandong and a subordinate of Zhang Zuolin.[23] Zhang Zongchang served as Nechaev's direct superior for the following years,[32] and allowed the Russian lieutenant general to operate largely autonomous. Nechaev selected several veteran White Russian officers for his staff, and some Chinese officers as interpreters.[33] Nechaev and his troops next took part in an expedition to conquer Shanghai from warlord Qi Xieyuan for the Fengtian clique.[34] By this time, the foreign legion already counted 800 officers, and 2,000 regular soldiers who had previously fought in the armies of Semyonov and Alexander Kolchak,[35] and four armoured trains.[36] The Russians fought with distinction at Wuxi and in the conquest of Shanghai in January 1925,[34][37] and then again when Sun Chuanfang, Qi Xieyuan's superior, attempted to retake Shanghai soon after.[35] As his forces were overextended, however, Zhang Zuolin had to withdraw from Shanghai in February.[38] Following the retreat, Nechaev suffered a major defeat, when he and one armoured train under his command were trapped near Suizhou. Their Chinese adversaries had pulled up the rail, and took this opportunity to massacre almost all mercenaries on board the train.[35] Nechaev managed to survive the incident, but lost a part of his leg during the bitter fighting.[35] Overall, the Russians earned a reputation as extremely capable fighting force,[32] becoming "Zhang Zongchang's crack troops",[39] but were also feared due to their high indiscipline[39][40][41] and extreme brutality against civilians and prisoners of war.[42][32] In November 1925, Leon Trotsky mentioned Nechaev in a speech to the Kislovodsk Soviet, claiming that he and his troops were paid by Great Britain to support Chinese monarchism.[43]

Despite his severe wound, Nechaev returned to duty in 1926,[35] and came to directly command the 65th Infantry Division, consisting of one Chinese and one Russian brigade.[42] The latter was about 3,765 men strong,[7] and was nicknamed the "Nechaev Brigade"[35][44] or "Nechaev Detachement".[12] He also remained the de facto commander of all Russian troops in the Fengtian foreign legion,[45] who counted about 5,270 overall by this point.[24][7] In early 1926 during the Anti-Fengtian War, Nechaev commanded one of his armoured trains in a battle against another armoured train in service of Feng Yuxiang. He managed to defeat Feng's train, which had been built by Soviet advisors.[27] Due to the increasing Soviet support for several enemies of the Fengtian clique in the late 1920s, Nechaev and the White Russians under his leadership increasingly perceived their mercenary service as "continuation of the holy war against Bolshevism".[35]

Later in 1926, Nechaev led three of his armoured trains on a rampage through the Chinese countryside, "machine-gunning civilians and stealing everything moveable". In an attempt to stop the White Russians, locals pulled up the railways, but this only resulted in Nechaev's forces sacking the nearest town.[32] Soon after, the 65th Infantry Division suffered heavy casualties in another armed conflict with Sun Chuanfang, so that "only several hundred" Russians were left in the unit by 1927, when war erupted between the Fengtian clique and the National Revolutionary Army (NRA) of the Kuomintang. Reduced in manpower, Nechaev and his forces mostly contributed to the Fengtian clique's resistance against the NRA's Northern Expedition by using their remaining armoured trains.[42] In March 1927, the Chinese Communist Party (CCP) launched an armed uprising in Shanghai against the local warlord garrison of Zhang Zongchang and Sun Chuanfang,[44] who had allied himself with the Fengtian clique to resist the NRA.[46] Nechaev's troops were among the 3,000 defenders of Shanghai's Zhabei district, and were only ousted from the city after heavy fighting with the CCP insurgents and NRA reinforcements.[47]

The war increasingly turned against the warlords, and the White Russians as well as their Chinese allies were steadily driven north by the NRA.[48] Following Zhang Zuolin's death in June 1928, his son Zhang Xueliang, the "Young Marshal", took over leadership of the Fengtian clique. He wanted to make peace with the NRA, and eventually fell out with Zhang Zongchang over this issue.[49][50] Nechaev's men still had at least three armoured trains under their control at the time, and initially assisted Zhang Zongchang in invading Manchuria to topple Xueliang. After crossing the Luan River, however, Zhang Zongchang was trapped by the now-allied troops of the NRA and the "Young Marshal"; realizing that the position of their superior was lost, the White Russians defected and turned the guns of their trains on their former allies. Zhang Zongchang was defeated, and the White Russian mercenaries were mostly demobilized thereafter.[50]