Why did Liu Bei warn Zhuge Liang that Ma Su could not be used before he died?

This is because Liu Bei had carefully observed Ma Di before and found that Ma Di could only talk and talk, just like Zhao Kuo, who talked about military affairs on paper. He could be a strategist, but if he was allowed to lead troops in war, , but it was going to cause serious problems, so before he died, he told Zhuge Liang that Ma Di had exaggerated and could not be reused.

Later, Ma Su really ruined the big thing. Zhuge Liang accepted Liu Bei's legacy and must regain the Han Dynasty and conquer the Central Plains. So after a period of intensive military preparation, he began the Northern Expedition.

In the early stage, the Shu army was overwhelming and captured several counties in the Wei state. However, the Shu army had a fatal weakness, which was the lack of food and grass. Therefore, as long as the food routes were controlled, the army could easily defeat the enemy. There is no harm. During the head-on confrontation between the Shu army and the Wei army that came to rescue, Zhuge Liang ordered Ma Su to guard the street pavilion. Street pavilion was an important grain road. Zhuge Liang repeatedly emphasized that the army must be stationed at the intersection.

Ma Di received the order and led the army to Jieting. When he arrived at Jieting, he found that there were high mountains on both sides of the road. Before that, he had been following Zhuge Liang to learn the art of war, and he thought he had learned from Zhuge Liang. strategy. He insisted on stationing his troops on two high mountains so that when the Wei army arrived, they could be caught off guard. The deputy general next to him advised him to listen to Zhuge Liang's order and station the army at the intersection, but he refused to listen. The Wei army cut off the only water source at the foot of the mountain. The Shu army on the mountain was extremely hungry and thirsty due to lack of water, and was defeated by the Wei army in one fell swoop. In this way, Ma Su lost his street pavilion. Zhuge Liang had no choice but to withdraw his troops and dispatched Ma Su militaryally.