Closing line of Wang Changling's (
王昌龄, Tang dynasty)
《从军行·其四》:
青海长云暗雪山,
孤城遥望玉门关。
黄沙百战穿金甲,
不破楼兰终不还 - 'Dark clouds over Qinghai darken the snowy peaks; from the lone frontier city one gazes at Yumen Pass. A hundred battles in yellow sand pierce our golden armor - we will not return until Loulan is broken.' Loulan was an oasis kingdom along the Silk Road, shorthand here for any western enemy.