What is the last sentence that yellow sand wears golden armor and never breaks Loulan?

The poem "Yellow Sand wears golden armor and never returns, Loulan can't return": The soldiers guarding the frontier have been through many battles, their armor is worn out, and they will never defeat the invading enemy and never return home. "Yellow sand wears golden armor in hundreds of battles, but Loulan can't be broken or returned" comes from "Joining the Army" written by Wang Changling, a poet in the Tang Dynasty, which expresses the lofty aspirations of the soldiers who vowed to pacify foreign aggression, and also expresses the poet's reverence and appreciation for the soldiers guarding the border.

Seven Military Songs (4)

Wang Changling [Tang Dynasty]

There is a dark snow-capped mountain in Qinghai, with long white clouds and a lonely city looking at Yumenguan.

Yellow sand wears golden armor in hundreds of battles, but the loulan is not returned.

Clouds are gathering over Qinghai Lake, covering the continuous snow-capped mountains. Looking at Yumen Xiongguan, the ancient city of frontier fortress, the soldiers guarding the frontier have been through many battles and their armor is worn out, vowing not to defeat the invading enemy and not to return to their hometown.

Appreciation of joining the army

The first two sentences of the poem, "There are dark snow-capped mountains in Qinghai, and the lonely city looks at Yumenguan", depict the desolate and vast scene of the northwest frontier and express the lonely mood of the frontier generals in their hard life. These three or four sentences, "Yellow sand wears golden armor in hundreds of battles, and Loulan breaks the square back", have changed from a description of the mixed environment to a direct lyric, showing the long time of guarding the border, the frequent wars, the hardships of fighting, the toughness of the enemy and the desolation of the border, and expressing the ambition of the soldiers to serve the country.

Writing background

Joining the Army was written in the prosperous Tang Dynasty, when the national strength was strong. However, the frontier is often invaded by nomadic peoples such as Tubo and Turkic, and the soldiers hope to defend the territory, defeat the enemy in the frontier and make the world peaceful. Wang Changling, a poet, was impressed by the great spirit of the times and wrote seven groups of poems "Joining the Army".