In 1926 Peng's forces joined the Kuomintang, and Peng was first introduced to communism.

Peng's experiences in the Korean War ( in which Chinese forces suffered over a million casualties, more than any other nation involved in the fighting ) convinced him that the Chinese military had to become more professional, organized, and well-equipped in order to prepare itself for the conditions of modern technical warfare.

When another civil war broke out in 1917, Peng's regiment split from the rest of its army and joined the forces of Tang Shengzhi, who was aligned with Tan Yankai and Sun Yat-sen, against those aligned with the northern warlord Wu Peifu.

Peng's forces then joined the Kuomintang, though Peng never joined the party as a formal member.

In July 22, 1928 Peng's forces, approximately 2000 men, occupied Pingjiang County, arresting and executing the county magistrate and over 100 landlords and local militia commanders.

On July 29 Peng's former superior, general Ho Chien, attacked Peng's forces, inflicting heavy casualties.

By September, Peng's forces were driven into the mountains, and by October only several hundred men remained.

Peng's forces successfully joined Mao and Zhu in November 1928.

After joining forces with communist guerrillas, one of Peng's first actions was to save Mao, whose forces were being encircled by Kuomintang units: Peng broke the encirclement and drove the enemy off.

In mid-1929 Peng's forces merged with the forces of two local bandit groups, but conflicts arose over supplies and the command structure, and the two groups rebelled against Peng in July 1929.

The remaining forces were incorporated into Peng's unit, bringing its strength up to 2, 000 men.

Peng's forces broke through the Kuomintang lines on July 28, and occupied Changsha proper on July 30, which Ho hastily evacuated.

Of the 18, 000 men under Peng's command when the March began, only about 3, 000 remained when Peng's forces reached their eventual destination in Shaanxi on October 20, 1935.

On May 4 Peng's forces attacked an isolated supply depot in northeastern Shaanxi, arrested its commander, and captured food reserves, 40, 000 army uniforms, and a collection of arms that included over a million pieces of artillery.

Peng's forces were pushed back to the border of Inner Mongolia, but finally managed to decisively defeat Hu's forces in August, in the Battle of Shachiatien, saving Mao and other members from the Central committee from being taken prisoner.

Between 1947 and September 22, 1949, Peng's forces occupied Gansu, Ningxia, and Qinghai.

In October Peng's forces, led directly by Wang Zhen, invaded Xinjiang.

Peng's forces continued their gradual occupation of Xinjiang, which they completed in September 1951.

Mao directed China's general strategy, and Zhou was appointed general commander, coordinating Peng's forces with the Soviet and North Korean governments, and the rest of the Chinese government.

Peng's operation was successful in disrupting Japanese communication lines and logistics networks, which were not fully restored until 1942, but the communists suffered heavy losses, suffering 22, 000 casualties to 4, 000 – 6, 000 Japanese casualties.

Most of Xinjiang's defenders surrendered peacefully, and were incorporated as a new unit in Peng's army, but some ethnic guerrilla bands resisted Chinese control for several years.

In the evaluation of Korean War historian Roy Edger Appleman, Peng's performances in the war were unremarkable in terms of military talents despite his aggressiveness and leadership skills.

During the Cultural Revolution, Red Guards claimed that Peng's successful campaigns, from October – December 1950, were fought under Mao's direction, but that his unsuccessful campaigns, from January – May 1951, were organized by Peng against Mao's instructions.

These perspectives, and Peng's long-held conviction that the primary role of the Communist Party was to improve the welfare of the common people, were contrary to Mao's political goals, contributing to their eventual conflict in the late 1950s.

When Peng's wife suggested the couple spend more free time visiting Mao's quarters, Peng was reluctant, stating that Mao's surroundings were " too luxuriously furnished " for him to tolerate.

PLA leaders were promoted into Peng's newly founded system of military ranks, and were awarded newly created orders of merit.

By September 1956 Peng's doctrines of professionalism, strict training, discipline, and the mastery of modern equipment were entrenched within the structure of the PLA.

Peng's position was not directly affected, but his personal prestige suffered, and the practical effects of his efforts to modernize China's armed forces were called into question within the PLA.

The other senior leaders of the Communist Party, including Zhou Enlai and Liu Shaoqi, were unwilling to risk splitting the Party, and sided with Mao in opposing Peng's position.

After Mao had rallied the rest of the Party against him, Peng's options were limited to stubbornly standing his ground, engaging in a humiliating self-criticism, or suicide.

In 1960 – 1961, the effects of Mao's economic policies continued to produce widespread economic collapse, improving Peng's reputation among Party leaders who secretly believed that Mao's policies were a mistake, and who desired to reverse them.

In practice, Peng's responsibilities were to oversee the industrial development of Sichuan, Guizhou, Yunnan, and Tibet, with a focus on developing military industries and logistical networks.

These positions were far below what Peng's position had been before 1959, but signaled his return to national politics.

Local Red Guards in Chengdu were not enthusiastic to follow these orders: they visited Peng's house on December 22, 1966 and attempted to intimidate Peng by informing him of the recent arrests of some of his friends and comrades, and of the imminent arrests of Liu Shaoqi and Deng Xiaoping.

Peng's bodyguards arrived to save Peng at around 4: 00 AM, but were already too late.

Peng's violent " interrogations " lasted over ten hours a day, but his interrogators were replaced every two hours in order to keep them from developing any sympathy for Peng ( a practice pioneered by Stalinist secret police in the 1930s ).

Peng's father was forced to sell most of his family possessions for food, and to pawn most of his family's land.

Peng's support for Mao's position changed the atmosphere of the meeting, and most leaders changed their positions to support a direct Chinese intervention in the Korean War.

" Mao purged most of Peng's supporters from important offices following the conference, almost completely isolating Peng politically for the rest of his life.

He became Peng's second-in-command, but spent most of the rest of the Chinese Civil War in central Party headquarters, in and around Yan ' an.

Lin reversed Peng's reforms, abolishing all signs and privileges of rank, purging officers considered sympathetic to the USSR, directing soldiers to work part-time as industrial and agricultural labourers, and indoctrinating the armed forces in Mao Zedong Thought.