Mankind knew the defensive effect of the city wall a long time ago. Since ancient times, there are many offensive and defensive battles which have been staged against the wall. When the Mongols began to fight in the world, the nomadic cavalry regiment that was good at field combat have no idea of siege tactics. But Mongols were good at learning, and they soon mastered the siege tactics and gathered siege weapons from all over the world for comprehensive use, achieving good results. Many solid cities were destroyed. At that time, the thinner walls in Europe could not resist the attack of the Mongols, especially the Mongols began to use a variety of powerful firearms which were more destructive. Since then, due to the improvement of artillery firepower, the role of the walls gradually disappeared from human history.
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How did firearms play a role in the siege.