Defensive wall
In mountainous terrain, defensive walls such as letzis were used in combination with castles to seal valleys from potential attack.
Beyond their defensive utility, many walls also had important symbolic functions – representing the status and independence of the communities they embraced.
The practice of building these massive walls, though having its origins in prehistory, was refined during the rise of city-states, and energetic wall-building continued into the medieval period and beyond in certain parts of Europe.
Simpler defensive walls of earth or stone, thrown up around hillforts, ringworks, early castles and the like, tend to be referred to as ramparts or banks.
The Assyrians deployed large labour forces to build new palaces, temples and defensive walls.
[2] Babylon was one of the most famous cities of the ancient world, especially as a result of the building program of Nebuchadnezzar, who expanded the walls and built the Ishtar Gate.
[3] Mundigak (c. 2500 BC) in present-day south-east Afghanistan has defensive walls and square bastions of sun dried bricks.
Likewise, the walls of the Forbidden City in Beijing were established in the early 15th century by the Yongle Emperor.
[7][8] Eupseongs (Hangul: 읍성), 'city fortresses', which served both military and administrative functions, have been constructed since the time of Silla until the end of the Joseon dynasty.
Part of the reason is probably because Chinese walls were already highly resistant to artillery and discouraged increasing the size of cannons.
[15] According to Philo the width of a wall had to be 4.5 metres (15 ft) thick to be able to withstand ancient (non-gunpowder) siege engines.
[16] European walls of the 1200s and 1300s could reach the Roman equivalents but rarely exceeded them in length, width, and height, remaining around 2 metres (6 ft 7 in) thick.
This held true into the twentieth century, when even modern explosive shells had some difficulty in breaking through tamped earth walls.
Famous military commanders such as Sun Tzu and Zheng Zhilong recommended not to directly attack cities and storm their walls.
During Koxinga's career, there is only one recorded case of capturing a settlement by bombarding its walls: the siege of Taizhou in 1658.
In 1662, the Dutch found that bombarding the walls of a town in Fujian Province had no effect and they focused on the gates instead just as in Chinese warfare.
In 1841, a 74-gun British warship bombarded a Chinese coastal fort near Guangzhou and found that it was "almost impervious to the efforts of horizontal fire.
"[22] In fact twentieth century explosive shells had some difficulty creating a breach in tamped earthen walls.
[23]As a response to gunpowder artillery, European fortifications began displaying architectural principles such as lower and thicker walls in the mid-1400s.
However, this proved problematic as the slow rate of fire, reverberating concussions, and noxious fumes produced greatly hindered defenders.
[24] In China, Sun Yuanhua advocated for the construction of angled bastion forts in his Xifashenji so that their cannons could better support each other.
Ma Weicheng built two bastion forts in his home county, which helped fend off a Qing incursion in 1638.
Furthermore, some street names hint at the presence of fortifications in times past, for example when words such as "wall" or "glacis" occur.
The top of the wall is often protruding and beset with barbed wire in order to make climbing them more difficult.
In addition to this, many different enhancements were made over the course of the centuries: The defensive towers of west and south European fortifications in the Middle Ages were often very regularly and uniformly constructed (cf.
Ávila, Provins), whereas Central European city walls tend to show a variety of different styles.
Apart from having a purely military and defensive purpose, towers also played a representative and artistic role in the conception of a fortified complex.
Furthermore, additional signaling and observation towers were frequently built outside the city, and were sometimes fortified in a castle-like fashion.
The border of the area of influence of the city was often partially or fully defended by elaborate ditches, walls and hedges.
An example of this practice is the Romanian Bran Castle, which was intended to protect nearby Kronstadt (today's Braşov).
