请将下面这段话翻译成英文：

　　张骞通西域

　　汉武帝时期，张骞两次出使西域，联合西域各国对抗匈奴。期间张骞曾两次被匈奴扣押，从未投降，逃出后拜访了大宛、康居、大月氏、大夏等国，加强了中国同中亚、西亚，以至南欧的直接交往。由于张骞所经过的地方都是汉人没有到过的地方，历史上称为“张骞凿空”。张骞第一次出使的报告记录在司马迁的《史记·大宛列传》中，至今仍是世界上研究上述地区和国家的古地理和历史的最珍贵的资料。

　　参考译文

　　Zhang Qian’s Missions to Western Regions

　　In the Period of Emperor Wu of the Han Dynasty, Zhang Qian was sent on missions to the western regions twice to ally with the states there to combat the Huns. During this period, Zhang Qian was taken into custody by the Huns but never surrendered to them. After he escaped from the Huns, he visited Dayuan, Kangju, Dayuezhi and Daxia. This strengthened the direct communications between China and Central Asia, West Asia and Southern Europe. Since the regions Zhang Qian visited were new to the Han people, this is historically known as "Zhangqian’s Trailblazing". Records of Zhang Qian’s first mission can be found in the Biography of Dayuan of Records of the Grand Historian authored by Sima Qian, which remains the most precious information on ancient geography and history of the above regions and states in the world.

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