I have only just finished reading the Introduction but I can already say that Hansen's book is far more engaging, focused, and informative than the disappointing tome by Peter Frankopan I read a few weeks ago.
This promises to be a good source on the history, geography, and trade along the Silk Roads.
Edit: This is an example of the type of information that I was missing in Frankopan's book:
The first written description of the Silk Road trade concerns Zhang Qian (d. 113 BCE), a Chinese envoy from Chang’an to Central Asia in the second century BCE, during the reign of Emperor Wu of the Han Dynasty (reigned 140–87 BCE). The emperor hoped that Zhang Qian would persuade the Yuezhi people, living in the Ferghana region of modern-day Uzbekistan, to ally with the Chinese against their common enemy to the north, the Xiongnu tribal confederation, based in modern-day Mongolia.
The earliest surviving account about Zhang Qian was written at least 150 years after his trip and does not provide many basic facts about his journey, such as his exact itinerary.
It is clear, though, that Zhang went through Xiongnu territory on his way to the Yuezhi. The Xiongnu imprisoned Zhang, and it took him about ten years to escape. Nonetheless, he still proceeded to visit the Yuezhi. On his return, sometime around 126 BCE, he gave the emperor the first detailed information the Chinese received about the different peoples of Central Asia. Zhang Qian was extremely surprised to discover that Chinese merchants and trade goods had preceded him to Central Asia. In the markets of Bactria, in modern-day northern Afghanistan, Zhang Qian saw bamboo and cloth manufactured in the Chinese province of Sichuan, several thousand miles away. The Chinese goods must have traveled overland.
After Zhang Qian’s return, the Han dynasty gradually extended its control into the northwest. By the end of the second century BCE it secured the Gansu corridor and Dunhuang. Each time the Chinese army conquered a new region, it constructed beacon towers at fixed intervals. If a disturbance occurred, the soldiers guarding the beacon tower lit torches to alert the men in the next tower, and so on down the line until the news reached the first garrison that could dispatch troops to the troubled area. In addition to the beacon towers, the Han military also established garrisons in the newly conquered territories. Documents in the form of bamboo slips recording army purchases of clothing and grain from the local people have been found at Juyan (Ejina Banner, Inner Mongolia, 90 km northeast ofJinta County, Gansu) and Shule (near Dunhuang and Jiuquan, Gansu).
The largest cache of early documents from the Silk Road was excavated from just such a Chinese garrison at Xuanquan, located 40 miles (64 kilometers) east of Dunhuang. A square dirt wall, 55 yards (50 meters) on each side, surrounded the complex, which had a stable for horses on its southern edge. Officials traveling on government business were entitled to get fresh mounts at the garrison, which also functioned as a postal station. On the northern and western edges of the enclosure were waste disposal areas; the western garbage pit extended 1.3 yards (1.2 m) underground at its greatest depth. The 2,650 artifacts from the site included coins, farm tools, weapons, iron cart parts, and utensils such as combs and chopsticks, as well as foodstuffs like grain, garlic, walnuts, almonds, and animal bones.
There are more than 35,000 discarded documents from the Xuanquan site: 23,000 wooden slips with Chinese characters on them, and 12,000 bamboo slips trimmed to size, apparently intended for later use. About two thousand of the slips bear dates between 111 BCE and 107 CE, the years when the garrison was in use.
The slips are written on wood and bamboo because paper was just spreading to Central Asia at this time. Invented in China during the second century BCE, paper was first used as a wrapping material and not for writing. The official histories record, for example, that in 12 BCE a murderer used poison wrapped in paper. Some of the earliest paper scraps found at Xuanquan, dating to the first century BCE, also bear the names of medicines, confirming the early use of paper as a wrapping material.
Not until four centuries later, in the second century CE, did paper come into widespread use as writing material in China. It took even longer for paper to replace wood and bamboo as the most common writing material along the Silk Road. Because paper was always expensive, people wrote on other materials like leather and tree bark. The documents at Xuanquan consist mostly of wooden slips tied together to form bunches (much like a placemat made from Popsicle sticks). The documents from the Xuanquan site include much everyday correspondence among the officials stationed at the Xuanquan postal station and other nearby locations, notices of new edicts issued by the emperor, announcements of runaway prisoners, and private letters. The scribes at Xuanquan distinguished among different types of wood: they reserved higher-quality pine for imperial edicts and used poplar and tamarisk, which warped easily, for routine documents and correspondence.