In the 15th century after the fall of Numenor the line of Elendil is in chaos. In 1409 the north kingdom of Arnor was ravaged by the Witch-King of Angmar, eventually to be repulsed by the Elves of Lorien, led by Elrond. The south-kingdom of Gondor had, at that time been ruled by Valacar for 50 years. It is Valacar's actions that led to "the first disaster of Gondor".
The story of the Numenoreans in Middle-Earth is one of decay and decline. At the end of the second age Numenor itself collapsed into the waves having been seduced by the deceits of Sauron. However Numenor was the centre of a vast empire and many numenoreans were left in diverse provinces across Middle-Earth. This included many so-called "Black Numenoreans" - followers of Sauron. It also included the followers of Elendil, called 'the Faithful' who had not succumbed to the lies of Sauron and who escaped the fall of Numenor in nine ships. It is from the heirs of Elendil that the kings of Gondor and Arnor claim their descent.
It is important to remember that the lifespan of the Numenoreans was much longer than that of the native men of middle-earth who lived under their rule. In the time of Valacar's father Gondor was harried from the North by the tribes of Rohan. An alliance was formed with Vidugavia, self-styled king of Rhovanion, as a result of which Valacar married Vidugavia's daughter Vidumavi. Unsurprisingly this alliance caused considerable concern in Gondor. For a race suffering decline in glory and lifespan the prospect of hastening this decline in the royal house through alliance with "lesser men" was most unwelcome. On Valacar's death there was rebellion in Gondor. In the end Eldacar was beseiged in Osgiliath, the capital city of Gondor, along with his son Ornendil. In the fall of Osgiliath, Eldacar escaped to his kinsmen in Rohan, however his son remained behind and was killed by Castamir (known as 'the Usurper' - but recall that the winners always get to write the history and in Tolkein's world Eldacar's faction definitely ended up on top), the leader of the opposition. Osgiliath was sacked in a fashion that "far exceeded the needs of war".
That's pretty much what you will learn from reading the appendices to Lord of the Rings. You can also find out what happened next but since I've absolutely no intention of adhering to the sequence of events should character actions dictate otherwise it won't necessarily help you much.
It should come as no surprise that many other social and economic factors contributed to the kin-strife. Chief among these was the tensions between the northern Gondorian cities (Minas Ithil, Osgiliath and Mina Arnor) with their interests and concerns based around Gondor's landward northern border with Rohan and the watch on Mordor and the southern cities (most notably Pelargir and Umbar) whose concerns were primarily maritime with large merchant classes interested in trade with the southern kingdoms of Harad and the large merchant city of Bozisha-Dar.
Caught between these two factions was the coastal northern territory of Dor-en-Ernil and its neighbouring territory of Morthond. Dor-en-ernil is strategically important because it fields one of the few mounted cavalry units available to the south kingdom. Adrazôr Lord of Lond Ernil remained neutral during the initial uprising. He sympathised with the concerns of the "traditionalists" but was loathe to engage in rebellion. He concentrated his efforts on trying to persuade Eldacar to step down in favour of a pure-blood alternative to Castamir. However many of his subjects were not so circumspect and the coatal town of Linhir rose in support of Castamir. This uprising was engendered by Calimon, Castimir's cousin. Adrazôr's nephew, Orodreth, heir to Morthond (a Gondorian territory west of Dor-en-Ernil) was a close friend of Eldacar's son Ornendil but nevertheless was salso ympathetic, to the traditionalist cause. Going against his uncle's commands Orodreth took control of the uprising in Linhir, partly to prevent Calimon gaining control and partly, seeing the way the wind was blowing, to protect his family's interests in the coming reign of Castamir.
Orodreth led his troops in the storming of Osgiliath and was first into the city and it was Orodreth who took his friend Ornendil's surrender. It was then that Calimon took his revenge. From his more secure position as one of Castamir's closest advisors, he accused Orodreth of conspiracy with Ornendil in Eldacar's escape. He was helped in this by three of Orodreth's captins who were able to supply sufficient evidence to qustion Orodreth's loyalty to Castamir. Calimon suggested that Orodreth now intended to spare Ornendil's life out of false "mercy" while all the time secretly working for the loyalist cause with no doubt an intent to assist in Ornendil's escape at a later point. Calimon suggested that Orodreth could only prove his loyalty by executing Ornendil. His hand forced, Orodreth felt he had no option. On seeing their prince, who had surrendered, killed in this summary fashion the people of Osgiliath rose in revolt thus providing the excuse for the rape of Osgiliath. This was 1437 and effectively concluded the rebellion with victory for the Traditionalist cause.
Horrified Orodreth renamed himself Neithan, self-wronged. Although his actions had secured Dor-en-Ernil and Morthond, he and his family were not trusted by Castamir. Castamir gave Neithan the post of Ethir Captain in the Anduin delta below Pelagir (now the de facto capital of Gondor). The Anduin delta is plagued by small-time smugglers and outlaw bands with which Neithan does not really have the resources to deal. It is here that he broods.
The characters all start out as people Neithan has cause to trust. His convoluted history means that characters may be sympathetic to either the Loyalist or Traditionalist causes but are unlikely to be fanatics on either side. Neithan travelled in his youth and may have met Gondorians from any part of their lands from Umbar in the south to Osgiliath and Minas Ithil. He may have visited the ravaged lands of Arnor in the north, or ventured further south into independent Numenorean colonies of Bellakar or to the Raj and its chief city of Bozisha-Dar. While he will have mostly mixed with pure blood Dunedain "nobility" he will also have known sea-captains, merchantmen and soldiers. In the chaos and confusion of the rape of Osgiliath all manner of people may have come to his attention, and in patrolling the Anduin delta he will have met smugglers, outlaws and many of the native Daen who, many thousand years previously, governed the realm of Gondor. The campaign predominantly takes place in the major cities of Gondor and so the characters will need to be prepared to spend much of their time in such places and not appear too out of place (so can we keep non-humans to a minimum please). While fighting will take place the emphasis will be on investigation. The characters need to be in or near the Anduin delta in 1441 either serving with Neithan on the river patrol or passing through on their way up-river to Pelargir.
MapHere is a map of Gondor I found while trawling the web.
You can't see Umbar (which is to the south) and many of the names have changed. Minas Arnor is called Minas Tirith on the Map and Lond Ernil is called Dol Amroth. Minas Ithil isn't shown on the map but it is the Minas Morgul of Lord of the Rings and is situated in Ithilien on the border of Morder basically in line with Minas Tirith and Osgiliath.
Diaries and Letters
NB. Although these may appear NPOV they include Ragnor's misunderstandings of the situation. Including some gross misunderstandings of court politics.