The moon, the front, the loneliness

Li Bai's version

To the Mournful Tune of Moon on Mt Guan
Li Bai 

The Tianshan Mountain moon
Rises bright
A sea of endless clouds
In the sky
Through Yumen Pass and back
Towards our homes
The long wind blows
A thousand miles

By Mount Baideng, we Han
Have marched the road 
The northern tribes invade
The Qinghai sea
So many men march out
But none return 
A battlefield for all
Eternity 

The border guards who watch 
Border towns
The grim desire for home
Is in their eyes
And back in lonely towers
This same night
The endless sound
Of tears and sighs 

李白  关山月
明月出天山，苍茫云海间。
长风几万里，吹度玉门关。
汉下白登道，胡窥青海湾。
由来征战地，不见有人还。
戍客望边邑，思归多苦颜。
高楼当此夜，叹息未应闲。

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I don’t know if this traditional version of the tune is what Li Bai would have heard, but it seems to capture the same mood.

Tianshan Mountains: These are a range of mountains in modern Xinjiang. The name translates as “Mountains of the Sky,” reflecting both that they are lofty and far away in the west, halfway to the netherworld. They are the mountains that soldiers might pass by on terrifying marches into unknown territory.

Yumen Pass: The mountain pass that marked the boundary between the Tang world and the deep west (the Tianshan Mountains were out in the deep west). In modern Gansu.

Mount Baideng: A mountain in the north of China where the Han emperor himself once led his troops against the Xiongnu of the Mongolian plains to the north.

Qinghai: The vast inland sea on the northern part of the Tibetan plateau, which lies to the west of the Tang Empire.

In this poem, Li lets his eye rove over the entire world. China’s invaders traditionally came from the north (Xiongnu/Huns, then the Mongolians, Jurchens, and Manchurians), the northwest (Central Asian Turks), and west (Tibetans). Li Bai marks out the points of the compass with geographical landmarks - each one with its own stock of historical tales of battle. The war is never ending: you defend the north, and they invade from the west.

Here’s a reconstructed reading.