In ancient times, wars were usually divided into field battles and hard battles. Fighting means that neither side will defend the city or attack each other between urban and rural areas. Hard fighting means that one side attacks the city and the other side defends it. Compared with the field battle, the tough battle is more difficult, with the highest tragic degree and more thorough destruction to the people. Siege attackers usually attack cities. In order to cut off the enemy's foreign aid or look for war preparations, the attacker will clear the surrounding areas of the city, and there will often be cases of disturbing the people and slaughtering. In order to maximize the potential of war, the defenders usually force the people in the city to join the army, or to serve hard labor, or to collect materials. The ancient generals who were good at guarding the city were Lian Po of Zhao and Zhang Xun of Tang Dynasty.

Lian Po was a famous soldier of Zhao at the end of the Warring States Period, and he was also called "Four Famous Soldiers of the Warring States Period" with Bai Qi, Wang Jian and Li Mu. Lian Po is brave and good at fighting. He has repeatedly made meritorious military service and is famous for his bravery. In the 16th year of Zhao Huiwen's reign (283 BC), Lian Po led Zhao Jun to March into the territory of Qi, captured the sublime princes, transferred troops from Lian Po to the DPRK, and formally worshipped Shangqing. That is to say, Lian Po's struggle for fame and fortune comes from the struggle against Qi. During the war, all the generals thought it was irreparable, and Lian Po was also afraid of Qin Jun and thought it was inappropriate to save Kui. Zhao She put forward the slogan "The brave win when the gorge meets the road", and led an army to kill hundreds of Qin Jun, thus relieving the siege. Qin sent his troops to attack several times. Lian Po bravely led the army to battle this time and defeated Qin Jun, becoming the second general of Zhao to defeat Qin Jun.

In the battle of Changping, Lian Po took the defensive according to the situation that the enemy was strong and we were weak, with the intention of dragging Qin Jun and winning the battle again. Lian Po correctly adopted the operational policy of establishing base areas to hold on, consuming the enemy and attacking the enemy with cameras. He ordered Zhao to build a tight barrier by virtue of mountain hazards. Despite Qin Jun's several challenges, Lian Po always shuts the crowd out. At the same time, the people in Shangdang area were concentrated, engaged in battlefield transportation, and committed to building fortifications against Qin. Zhao heavily guarded, unable to meet the challenge, and his spirit gradually lost. In order to defeat Qin Jun's plan of a quick victory, Lian Po fought hard and persisted for three years. Facing Lian Po's strict defense, Tian Lei, the god of war of Qin, could do nothing. Finally, he used double agents to make Zhao change his mind and won the battle of Changping.

Zhang Xun, a native of Hedong, Zhou Pu, was a famous soldier in the middle Tang Dynasty. At the end of the kaiyuan reign of Emperor Xuanzong of the Tang Dynasty, he was a scholar in Zhang Xun and served as a prince, counselor, Qinghe county magistrate and Zhenyuan county magistrate. During the Anshi Rebellion, Zhang Xun set out to defend Qiu Yong against the rebels. In February 756 AD, Ling led fifteen thousand Yan troops back, and Zhang Xun defended the city and defeated the Yan army. In March of the same year, Chao and Yan generals Li Huaixian, Yang Chaozong and others led more than 40,000 people to Enemy at the Gates in an attempt to capture the city in one fell swoop. Zhang Xun defended the city, being both wise and brave, and defeated the Yan army many times. During the defending battle of Suiyang, thousands of Zhang Xun resisted more than 100,000 Yanjun for two years. Although he failed in the end, he still went down in history.