Possibly the most significant event in the history of the world so far, The Longest Night was a cruel and horrible winter that lasted an entire generation, where the sun rarely shone and the world of the living was assaulted by famine, winter storms, and The Others. Scholars call the Longest Night 28 years long, measured from the first frost in Oldtown to the retreat of the White Walkers in the Battle for the Dawn. The reality of this horrible season is different for every kingdom in the world, however. While the people of The North and The Iron Islands suffered most cruelly, other far-flung nations such as Ib and Andalos also were battered by the unrelenting fury of its brutal cold. Meanwhile, some lucky kingdoms such as Dorne, the Summer Islands, and The Valyrian Freehold remained insulated from most of the winter’s hardships.
Although the plummeting temperatures and mounting snows were a challenge, and the shortages in food grew ever worse as the years passed, the most terrifying hazard of the Longest Night was the Others and their undead army of wights, ice spiders, and revenant beasts. In this, it was Westeros alone that suffered, for the Land of Always Winter has but one means of connection to the world of the living, and that is The North.
It was in the seventeenth year of the Longest Night that they were first acknowledged by the King of Winter, although certainly the White Walkers had been preying upon men for years before that, thinning the ranks of the living and adding wights to their armies. Robert Stark called his banners and sent ravens to the Southron kingdoms, and the war against the Others had begun. It did not take long for the soldiers of mankind to realize that no common weapons could harm the Others. Any sword might hack a wight to pieces, and fire was effective against all of the undead, but the White Walkers possessed some mystical quality that made them proof against nearly all of the weapons of the age. Valyrian steel and dragonglass proved to be the only weapons that were proof against the magical unlife of the Others, and would end them almost instantly. The forces of Westeros, marshalled by the King of Winter, scrambled to collect as many weapons of Valyrian steel as could be found.
To signify the unity of the kingdoms of men against the undead, a military order was founded wherein the men who joined gave up all titles and claims to inheritance, vowing to guard the realms of men until the end of their days. The Night’s Watch were one of the most crucial components of the long fight to hold back the tide of the White Walkers attempting to invade the world of men.