Great Wall as a defensive project consists of three parts pass, walls, watchtowers composition.

Wall pass

Pass an important garrison stronghold along the Great Wall, the Great Wall and out of position more choice in the throat thoroughfare. Pass the entire structure, typically by the crossing square or polygonal walls, gates, gate building, Urn composition. Rochester and some have a moat.

① walls. Great Wall of major projects, particularly strong, both inside and outside the parapet multi giant brick, stone and other masonry bag, filled with loess, gravel, height is generally around 10 meters. Top width of 4 to 5 m, and the upper and lower walls of the galleries and stairways. On the eave walls built forts and look for lance shooting, including canopies built with walls about one meter high wall of buildings (or woman called wall) to protect the troops will not fall from the top of the wall.

② gates. Is usually out of the channel crossings, to counter the enemy in wartime is exports. Openings built huge double-leaf doors, door and inner door with the lock ring.

③ gate towers. Above the gates were built a gate building, it is the battle of observation and command posts, also fighting positions. Gate towers, mostly wooden structures and brick buildings one, two or three layers.

④ Urn. Contemplated in the main direction of the enemy outside the gates and then build a "П" shaped walls forming two walls, which is to increase the role of defense in depth, to strengthen the defenses of the gates.

⑤ Rochester. Is expected outside the main direction of the enemy Urn, and then build a "П" shaped walls, it is relatively long, in addition to the cover of the Barbican, but also can cover a longer inner city walls lot. In Rochester walls, generally built tower to observe the enemy, command operations. At both ends of the walls, built a watchtower, and hope to enhance the lance patrols.

⑥ moat. Chengguan are generally moat around the city and is off line of defense. It is formed when digging earthwork fortification, and later reintroduced river.

Great Wall Walls

Walls are linking with big, Pass, and other enemy units. An average of about 7 to 8 meters in a steep hill where a relatively low walls. Is a defensive body walls, base wall average width of 6.5 meters, 5.8 meters wide at the top, at the culmination of small trapezoidal cross section, so that stability is not easy collapse. Wall structure, according to local natural conditions, the main version built of rammed earth wall, and assembled adobe walls, brick walls, mixed masonry walls, stone walls and palisade wall and assembled wood preparation, wood-paneled walls and so on. In addition to the main walls of the city walls, there are even a lot of construction facilities. ① coupons door. In the side walls of the back side, there is a short interval of brick or stone arch, said circular coupons door.

Coupons door with brick or stone staircase through to the top of the walls, soldiers guarding the city can thus be up and down. ② forts. Against them in the direction of the top outside the city, repair a toothed crenellations about 2 meters high (i.e., crenellations). The upper part of each forts have a small mouth mouth Wang called lance for lance hope the invading enemy; the lower forts there is a small hole, called the shooting eye for shooting enemies. ③ city of Taiwan. On the outside walls of every 200 to 300 meters above the top of the walls built with a surface of about 1 m in the table, in the projecting direction to meet the enemy walls. Build forts outside of wartime condescending, shot from the flank wall boarding ladder rack enemies.

According to various city stations use to build a case into the wall units and enemy units. Wall table tops and walls top height difference is not big, but the protruding part of the wall on the outside lined with battlements is usually on patrol sentry city Shoubing place. The platform also has a simple houses shelter, called the shop room. That fence piers enemy units, higher than the top of the walls, there are two or three layers. Defenders soldiers can live there, and store weapons and ammunition. Multisection Badaling enemy units at upper and lower layers, the lower layer may have been 10 Yushi Cu, surrounded by the window for observation and firing, wooden stairs to board the roof, roof ground level, surrounded by walls forts, and look for lance shooting. In addition, there are on the walls of the wall drains, used to drain the water at the top of the walls to protect the walls.

- Beacon -

Beacon also known as beacons, Feng Baihe, Taiwan Feng, Beacon, pier, wolf Yantai, Pavilion, Sui and so on. Is the use of flames, smoke to pass military intelligence building. In cases where the enemy, daytime burning cigarette (flags can also be hung, knock bang, blasting), using fire at night (or lantern on point). Beacon is usually provided on the Great Wall and the most vulnerable lance beheld the top of the hill, usually with earthen or stone into a separate high-profile, there are watch houses burn and smoke fire equipment on the table, the table below house soldiers guarding the residence and Yang Ma circle, barns and other buildings.

- City, Fort barrier, Baihe -

In the Great Wall defense system works, there are some associated with the Great Wall of the city, Fort barrier, Baihe and other buildings. Most of these buildings building both inside and outside the Great Wall, for residential and defensive pawns. Here the meaning of "city", is not a state, county, town, but the area associated with the Great Wall of defensive architecture, the city is small, ranging from dozens of miles away between the city and the city. "Barrier", is also a town. Some say the ancient literature is the mountain town. The distinction between "barrier" and "City" are the "city" of different sizes, there are residents living in the "city" and "barrier" to live only soldiers, residents live, more unified barrier of size and form.

There is also the city and the barrier together, both live his soldiers, and non-residents. "Baihe" that waiting, also known as "Scout" is a watchman for building, construction is relatively simple, often used in conjunction with the kiosk (Beacon), often "pavilion waiting" and said. Ming's "Castle" and the city of Han Dynasty "city barrier" is similar, but also for the garrison, "Castle" is often surrounded by walls, also known as the castle. There are some Baonei Beacon, residents also live there. Along the city wall of the Ming and more combined with the mark to plug and fight the enemy invasion.

- defense system -

Great Wall has the entire layout trunk, branches there, many barriers set up along the route, Fort buildings, enemy units, beacon towers and so on different levels, in different forms and different functions, constitute a complete defense system. This system every small military base layers are associated with the administration and central government agencies through. From the perspective of defense, usually divided into several zones along the Great Wall. Qin Shi Huang period, the establishment of Longxi, north, Kamigori, nine of the original, cloud, Yanmen, Yamanashi, on the valley, Yu Yang, right Peking, western Liaoning, Liaodong in 12 counties on the route of the Great Wall, to the jurisdiction of places along the Great Wall , segmented defense. To facilitate Ming along the Great Wall of defense, the defense is divided into nine sections, called "Nine", guarding provided on each side (commander), i.e. Liaodong, thistle, Xuanfu, Pax, Taiyuan Yansui Ningxia, Guyuan, Gansu nine towns, that of the nine Important. Ninety-nine outside edge of the town, in order to strengthen the defense and protection of the capital Mausoleum (next Tombs) needs to Jiajing three years (1551) and in the northwest of Beijing and the addition of dachangzhen really protect the town, a total of eleven the town, the town constitutes a nine eleven defensive layout.

--historical meaning--

The Great Wall built more than 2,000 years ago, though already out of action on defense, but still stand tall, displayed Chinese long history, reflects the great achievements of China's ancient architecture engineering technology, performance perseverance of all ethnic groups of the working people in ancient China and wisdom, reflects the strategic thinking of active defense of China since ancient times formed. In addition to the Great Wall as a historical scale, the areas along the Great Wall for the study of changes in the natural environment and natural events provide a reference. Wall massive and grand scale, reflecting the grandeur of the Chinese nation, a symbol of ancient Chinese culture. After finishing the ancient Great Wall, many sections become a tourist attraction. Shanhaiguan, 3 Badaling and Jiayuguan City Commissioner segment in 1961 was designated as the Chinese national key cultural relics protection units. It has been listed as a UNESCO World Heritage Site.