How to appreciate "the dusty day in the desert is faint, and the red flag is half rolled out of Yuanmen"?

Origin: The fifth of Wang Changling's seven poems about joining the army in the Tang Dynasty, the whole poem is:

The desert is foggy, and the red flag is half rolled out of Yuanmen.

The former army fought in Taohe River overnight, and it was reported that Tuguhun was captured alive.

In the desert, the wind and sand are all over the sky. It's getting dark The red flag was rolled on the flagpole, and the soldiers went out of Yuanmen, ready to March.

Appreciation: This sentence comprehensively describes the scene on the battlefield. The previous sentence is about the prospect, "desert" refers to the place, and "dust" refers to the weather. Twilight is a scene in which yellow sand covered the sky at that time. Not only wrote the desert climate, but also wrote the scene of yellow sand all over the sky It also highlights the tension in the battlefield situation. It embodies the fearless spirit of soldiers on the battlefield. The close-up is written in the next sentence. "Yuanmen" refers to the gate of the camp, and "out of Yuanmen" means that the army wants to touch it. "Red flag half-rolled" means that the red flag winds around the flagpole and travels in the wind. The rapid advance of the army shows the fierceness of the front-line battles and the strength of the enemy. "Half-volume" corresponds to the "wind" in the previous sentence. Here, the departure of the army was implicitly hinted by the red flag out of Yuanmen. This shows the tension of the coming war.