The Song dynasty ([s]; Chinese: ; pinyin: Sng cho; 9601279) was an imperial dynasty of China that began in 960 and lasted until 1279. The dynasty was founded by Emperor Taizu of Song following his usurpation of the throne of the Later Zhou, ending the Five Dynasties and Ten Kingdoms period. The Song often came into conflict with the contemporaneous Liao, Western Xia and Jin dynasties in northern China. After decades of armed resistance defending southern China, it was eventually conquered by the Mongol-led Yuan dynasty.

The dynasty is divided into two periods: Northern Song and Southern Song. During the Northern Song (Chinese: ; 9601127), the capital was in the northern city of Bianjing (now Kaifeng) and the dynasty controlled most of what is now Eastern China. The Southern Song (Chinese: ; 11271279) refers to the period after the Song lost control of its northern half to the Jurchen-led Jin dynasty in the JinSong Wars. At that time, the Song court retreated south of the Yangtze and established its capital at Lin'an (now Hangzhou). Although the Song dynasty had lost control of the traditional Chinese heartlands around the Yellow River, the Southern Song Empire contained a large population and productive agricultural land, sustaining a robust economy. In 1234, the Jin dynasty was conquered by the Mongols, who took control of northern China, maintaining uneasy relations with the Southern Song. Mngke Khan, the fourth Great Khan of the Mongol Empire, died in 1259 while besieging the mountain castle Diaoyucheng, Chongqing. His younger brother Kublai Khan was proclaimed the new Great Khan and in 1271 founded the Yuan dynasty. After two decades of sporadic warfare, Kublai Khan's armies conquered the Song dynasty in 1279 after defeating the Southern Song in the Battle of Yamen, and reunited China under the Yuan dynasty.Technology, science, philosophy, mathematics, and engineering flourished during the Song era. The Song dynasty was the first in world history to issue banknotes or true paper money and the first Chinese government to establish a permanent standing navy. This dynasty saw the first recorded chemical formula of gunpowder, the invention of gunpowder weapons such as fire arrows, bombs, and the fire lance. It also saw the first discernment of true north using a compass, first recorded description of the pound lock, and improved designs of astronomical clocks. Economically, the Song dynasty was unparalleled with a gross domestic product three times larger than that of Europe during the 12th century. China's population doubled in size between the 10th and 11th centuries. This growth was made possible by expanded rice cultivation, use of early-ripening rice from Southeast and South Asia, and production of widespread food surpluses. The Northern Song census recorded 20 million households, double of the Han and Tang dynasties. It is estimated that the Northern Song had a population of 90 million people, and 200 million by the time of the Ming dynasty. This dramatic increase of population fomented an economic revolution in pre-modern China.

The expansion of the population, growth of cities, and emergence of a national economy led to the gradual withdrawal of the central government from direct involvement in economic affairs. The lower gentry assumed a larger role in local administration and affairs. Social life during the Song was vibrant. Citizens gathered to view and trade precious artworks, the populace intermingled at public festivals and private clubs, and cities had lively entertainment quarters. The spread of literature and knowledge was enhanced by the rapid expansion of woodblock printing and the 11th-century invention of movable-type printing. Philosophers such as Cheng Yi and Zhu Xi reinvigorated Confucianism with new commentary, infused with Buddhist ideals, and emphasized a new organization of classic texts that established the doctrine of Neo-Confucianism. Although civil service examinations had existed since the Sui dynasty, they became much more prominent in the Song period. Officials gaining power through imperial examination led to a shift from a military-aristocratic elite to a scholar-bureaucratic elite.

A crossbow is a ranged weapon using an elastic launching device consisting of a bow-like assembly called a prod, mounted horizontally on a main frame called a tiller, which is hand-held in a similar fashion to the stock of a long firearm. Crossbows shoot arrow-like projectiles called bolts or quarrels. A person who shoots crossbow is called a crossbowman or an arbalist (after the arbalest, a European crossbow variant used during the 12th century).Although crossbows and bows use the same launch principle, the difference is that an archer must maintain a bow's draw manually by pitching the bowstring with fingers, pulling it back with arm and back muscles and then holding that same form in order to aim (which distresses the body and demands significant physical strength and stamina); while a crossbow utilizes a locking mechanism to maintain the draw, limiting the shooter's exertion to only pulling the string into lock and then releasing the shot via depressing a lever/trigger. This not only enables a crossbowman to handle stronger draw weight, but also to hold for longer with significantly less physical strain, thus potentially achieving better precision.

Historically, crossbows played a significant role in the warfare of East Asia and Europe. The earliest known crossbows were invented in the first millennium BC, not later than the 7th century BC in ancient China, not later than the 1st century AD in Greece (as the gastraphetes). Crossbows brought about a major shift in the role of projectile weaponry in wars, such as during Qin's unification wars and later the Han campaigns against northern nomads and western states. The medieval European crossbow was called by many names, including "crossbow" itself; most of these names derived from the word ballista, an ancient Greek torsion siege engine similar in appearance but different in design principle. The traditional bow and arrow had long been a specialized weapon that required considerable training, physical strength, and expertise to operate with any degree of practical efficiency. Many cultures treated archers as a separate and superior warrior caste, despite usually being drawn from the common class, as their archery skill-set was essentially trained and strengthened from early childhood (similar to many cavalry-oriented cultures) and was impossible to reproduce outside a pre-established cultural tradition, which many cultures lacked. In contrast, the crossbow was the first ranged weapon to be simple, cheap and physically undemanding enough to be operated by large numbers of untrained conscript soldiers, thus enabling virtually any military body to field a potent force of crossbowmen with little expense beyond the cost of the weapons themselves.In modern times, firearms have largely supplanted bows and crossbows as weapons of warfare. However, crossbows still remain widely used for competitive shooting sports and hunting, or for relatively silent shooting.It is possible to turn at least some store-bought bows into a crossbow. It is done by marrying a stock-and-trigger system to a bow.