In June 1946 the Kuomintang tore up the cease-fire agreement and launched all-out civil war. The main force of the Shanxi-Hebei-Shandong-Henan Field Army commanded by Liu and Deng engaged in mobile warfare on both sides of the Longhai Railway. Advancing and withdrawing over great distances, they fought nine big engagements in quick succession, at Longhai, Dingtao, Juye and other places, annihilating large numbers of Kuomintang effective.

The situation was still grave when the War of Liberation entered its second year. The Kuomintang army, though greatly weakened, was still nearly twice as large as the People's Liberation Army and vastly superior in arms and equipment. In an attempt to take the war deep into the liberated areas, it was making heavy attacks on key points in Shandong and northern Shaanxi. In light of the new overall situation, the Communist Party led by Mao Zedong decided to pass immediately from strategic defense to strategic offense, without waiting to have smashed the enemy attack and gained superiority over the Kuomintang. Focusing its attack on the Central Plains, where the enemy was weak, and shifting to exterior-line operations, the PAL would thrust directly to the enemy's rear, hoping to bring about a strategic change in the war situation.

According to the Central Committee's plan, it was the main force of the Shanxi-Hebei-Shandong-Henan Field Army under the command of Liu Bocheng and Deng Xiaoping that was to carry out this crucial mission. At the end of June 1947, in a surprise move, Liu and Deng, with an army of 120,000, crossed the dangerous Huanghe (Yellow River) and entered southwestern Shandong. In 28 days of continuous fighting they routed 56,000 enemy troops, thus clearing the way for their march south. They decided that instead of leaving contingents behind to secure each city they took, they would press forward by forced marches. In 20-odd days, despite blocking and pursuit by hundreds of thousands of enemy troops, they crossed the Longhai railway and covered a distance of 500 kilometers, traversing the marshy 15-kilometer floodplain of the Huanghe, wading the Shahe, Ruhe and Huaihe rivers and finally reaching the Dabie Mountains on the borders of Hubei, Henan and Anhui provinces.

From their position in the Dabie Mountains north of the Changjiang (Yangtze River), the enemy under Liu and Deng posed a direct threat to the vast Kuomintang areas south of the river, including Nanjing in the east and Wuhan in the west. The Kuomintang was obliged to assemble its main forces to defend the area and encircled the Dabie Mountain region with 30 bridges numbering 200,000 men. The troops under Liu and Deng were exhausted from continuous marching and fighting and were unfamiliar with the terrain. Furthermore, since they had only just arrived in the new area, they had no time to set up local governments and mobilize the people, so they were short of food, clothing and ammunition. Liu Bocheng took command of part of the force and broke through the encirclement to build new base areas along the western reaches of the Huaihe River, while Deng Xiaoping and Li Xiannian, Deputy Commander of the Central Plains Military Command, were left to command a crack force whose task was to continue stubborn resistance in the mountains. Calling on the soldiers to be selfless, Deng said that there were two loads to be selfless, Deng said that there were two loads to be carried, and one was heavier than the other. If they in the Dabie Mountains carried the heavier load, other armies another regions would be able to destroy large numbers of enemy troops and carry out intensive work among the masses, which would be greatly to the general advantage. They should therefore hold on firmly, no matter how weak they became and what hardships they had to endure. Sharing the hardest conditions with their men, Deng and Li maneuvered in the mountain gullies day and night, often on empty stomachs. They divided their forces into smaller units, some to deal with the enemy's local "peace preservation corps" and others to engage in grassroots political work. If a large enemy force was approaching, they would concentrate part of their troops to attack it. Meantime, they mobilized the people to struggle against despotic feudal landlords and organized local armed forces and militia, thus establishing a solid base in the Dabie Mountains.