The Night's Watch is an ancient military order dedicated to holding The Wall, the immense fortification on the northern border of The North, defending the realms of men from what lies beyond it.The men of the Night's Watch are allowed to wear only black.
The Night's Watch is one of the oldest orders in the Seven Kingdoms, as it survived the fall of the kingdoms of the First Men, following the Andal Invasion and the Aegon's War of Conquest. It was founded over 8,000 years ago, at the end of the Long Night. Under cover of an endless night that lasted for a generation, the Others invaded from the Lands of always Winter, laying waste to much of Westeros, until the Others were finally defeated by the Night's Watch at the Battle for the Dawn. After having pushed back the threat, the Wall was allegedly built by Bran The Builder in order to protect the Seven Kingdoms, should the Others ever return. During the Age of Heroes it was also recorded that the children of the forest gave the Night's Watch a hundred obsidian daggers every year.
Other than the corrupting of the thirteenth Lord Commander, the "Night's King" further attacks by the Others never came, however. Instead, the most frequent attacks came from the wildlings, sometimes led by their kings, and their constant attempts at raiding in the North. Little by little, the Night's Watch began to forget that its main mission was not the fight against the wildlings, but against the Others. As the years came and went, the purpose of the Watch became less and less obvious, and its manpower decreased more and more, with most of Westeros neglecting the Wall. Only the North, particularly the Starks, have the memory of the old days, but even they believe the Others are no more than vague figures in stories told to frighten children.
The Night's Watch has built nineteen castles along the hundred leagues of the Wall. At the zenith of its power, the Watch had seventeen of the castles manned, with over ten thousand men-at-arms between them. Castle Black alone quartered five thousand fighting men with all their horses, servants, and equipment. The highborn of the North have traditionally considered it an honor to serve on the Wall. Many younger sons of northern houses, low in the line of succession, gladly took the black. Shields of nobles were proudly displayed in the Shieldhall at Castle Black. By 297 AC, however, only three castles remain in use and the Night's Watch's numbers have dwindled to fewer than a thousand men. The Night's Watch is now largely made up of the misfits of the Seven Kingdoms: peasants, debtors, poachers, rapers, thieves, and bastards. Only a few of the noble and knightly houses south of the Neck have members in the Night's Watch, and most serve because they fell afoul of political machinations or fought on the wrong side of a war. However, there have been fewer wars since the War of Conquest and the subjugation of the Seven Kingdoms to the Iron Throne.