The Union of Númenor began shortly after the coronation of Skelesam as 2nd Chieftan of Arnor, and Atanvarno 5th King of Gondor. Shortly after the Union began, the Shire under Thain_Vibiras also joined, adding further to the strength of the Union. Following the conquest of Umbar, they too joined the Union.
The aim of this Union is to unite the Dúnedain of the North and South to create an even larger force to work for the Good of Middle Earth, and defend it from those who would see the Free People harmed.
The ancient kingdom of Gondor was one of the two founding factions in the Union Of Númenor. Comprising the Dúnedain of the South, Gondor is constantly on alert for the Shadow in the East.
The other founding faction was Arnor, more commonly known as the Rangers of the North. The shattered kingdom of Arnor is made up of the Dúnedain of the North and have long watched over the lands of Eriador and remained vigilant against the hordes of Gundabad and Angmar.
The Little Folk of the Shire, the Hobbits. The Shire was the 3rd faction to join the Union. Relations between the Shire and the Dúnedain have long been friendly so the Shire was quick to be welcomed in and became instrumental in Númenor's decisions.
Following the War Of Reconquest, Umbar surrendered and joined Númenor. The capital was being built by Kvesir and another city was being built by Thain_Vibiras. Following the expulsion of Kvesir and his Corsairs after they were found to be traitors Númenor, Thains city became the capitol of Umbar.
Story about the founding of the Union
The man stood silently upon the hill, his face carved by wind and sun, standing as an ancient guardian stone watching the lands. His face was facing south, from where he saw a lonely rider passing the open plains. For a while, the man watched him growing and growing, as he drew near. When he was at the distance the man could see the white tree carved on his chestplate, the man sighed of relief as he thought the King of Gondor would not have reached his letter. For the rider now climbing up the hill, was King Atanvarno II, Fifth ruler of Gondor and his old friend and companion. He started walking down the hill, as Atanvarno dismounted from his horse and walked towards Skelesam, Chief of the Dúnedain. They greeted each other as old friends, not as leaders of two factions, and you could see from the look on their faces they had been through much together, and would do it all again to save each other. "Brother", Atanvarno said. "What troubles you so much that I have to ride North to speak with you? For I am glad to see you, but you look troubled, and I can clearly see that time has not spared you, as you look twice as old as I remember you". "Troubled I am, Atan. For my mind is filled with sadness and despair. Time indeed has not spared me, as since the disappearance of our Chief, Combobob and I have had our hands full on bands of Goblins and Orcs pouring down from the Misties. Their numbers increase everyday, and I am afraid we cannot hold them if that day comes. Plague has felled many good men, and as strong and valiant as we are, even we can die." This news troubled Atanvarno, as the Dúnedain are kin, and every loss of them gave him the feeling the Line of Kings has truly failed. "This news does not bode well, old friend. I am sorry to hear this, and if there is anything I could do to help, you just say so." Atanvarno looked into the eyes of the man he had followed for so long, who had stood beside him for so long, facing countless dangers. A silence followed, and was broken a few moments later by Skelesam, who said: "Oh King of Gondor. I stand here humble, not as equal, but as a brother asking for help. I want to see Arnor prosper again as it did from Old. I want to see our banners on the high hill, as we fight against the endless hordes of enemies, be it Orc or Man. I want the old Realm of Númenor back, stretching from the North to Umbar in the South. I want my people to grow old in peace, in the cities of Fornost, Annúminas and Tharbad, knowing they live safe. I want many things, but what I mostly want, is to whipe away the Darkness from our lands. So let us do this together, or fail together". A long silence followed. "Let our swords shine bright in the sunlight, as we drive off the Orc armies of the Misties, the Uruk-Hai of Isengard and the foul Southrons! Let our drums bring fear into our enemies' hearts, as they know only death follows those sounds. Let our merchants trade with all Free Peoples, and our children to grow strong and proud, as the great Kings of Old! Let us unite under one banner, the banner of the Númenoreans, of Gondor and of Arnor! " And so the Union was followed, and once again their people stood proud and tall, facing the threats on the borders head on. They drove back the Goblin war bands and made the greenway road safe for traders. And they fought many battles, until the gates of Umbar.
The end of the Union came when the Arnorian Chieftain Elendil_The_Tall withdrew from the Union. Following Arnor's withdrawal, Numenorian Umbar was made directly part of Gondor, and the alliance became between only Gondor and the Hobbits. While this lasted for a time, the two parties finally decided to end the declining Union, and it at last was disbanded.