Far Harad
Little enough is known of the Haradrim from Tolkien's writings. But there seem to have been many groups, or tribes, or kingdoms among the people living generally south of Mordor, so the inclusion of the Principality of Far Harad (as well as the Principality of Harondor) is one way the dev team of the Fourth Age: Total War chose to represent what may have been a more chaotic political situation in the South than can be perceived by simply looking at a map.
The team opted to portray Far Harad as a desert realm ruled by a Prince, ever in danger of being drawn into the orbit of the Empire of Harad. These people seldom came into contact with others north of the Poros (though the Southron Champions who hail from these distant lands are much prized by the Empire – and much feared by their foes). The great distance from other factions means that the Prince of Far Harad is freer to choose his allies than, say, the Empire of Harad, with its long history of wars and grievances.
On the other hand, Far Harad shares some of the strategic concerns of Khand: the land is open, with no rivers, forests, or mountains to use as a defensive barrier. Some independent settlements to the north are all that stand between Far Harad and Khand; and to the northwest, nothing but a short march of desert and scrubland separates Far Harad from its much larger and more powerful neighbor, the Empire of Harad.
A war with both Khand and the Empire is almost certain; the only question is who will strike first. And for much of the game, Far Harad's chief concern will be managing the course of this two-pronged war.
Fortunately, Far Harad boasts a varied and balanced unit roster that is well-suited to the desert fighting ahead. With its combination of efficient archers, infantry, and light but hard-hitting cavalry, Far Harad's armies can meet a variety of threats. Some notable units include the Southron Champions, whose great size and strength allows them to cut through lesser troops with ease, and the several skirmisher types available for training or hire, who can thin the ranks of the foe and then fall upon the enemy's flanks.
As the larger of the enemy factions, the Empire of Harad is probably the greater threat. Their units are similar to yours, but they are able to outproduce you, so you will need to rely on your mastery of tactics in order to defeat their greater numbers. That said, it may not be enough to simply play defense against the Empire, since they will win a war of attrition. A Prince of Far Harad who wants to end the threat to his sovereignty decisively will need to be aggressive, bursting out of the desert with raiding forces to attack the Emperor's armies before they arrive, and in some cases sacking Imperial settlements, then fading back into the sands with baggage trains full of booty and slaves before the counter-blow can be struck. The Empire is likely to be busy dealing with the other unruly realm on its border, the Principality of Harondor, so timing your strikes well may allow you to conquer several new territories.
After you have captured some Imperial towns and seen a few victories on the battlefield, emissaries may arrive from Umbar with a demand that you submit to the Emperor's overlordship. This is an offer worth considering. Such arrangements are often short-lived, but can buy you time to train fresh warriors and position them near rich Haradrian cities, ready to fall upon them as soon as the treaty lies in tatters – or sooner!
Your other chief rival, Khand, tends to field many horse archers, which can be murderous on an open field. City defenses are much more favorable, but of course the settlements Khand is most likely to attack are those in your homelands, which you depend upon for income and training. Sooner or later, Khand will have to be dealt with as well.
The uniqueness of Far Harad is its isolation from the central wars of the map. While you have been fighting for your survival in the far South, kingdoms in the northern lands have risen and fallen, dynasties have been snuffed out, new realms are being built. The Chiefdom of Rhun, swollen with warriors eager for plunder, may hold lands stretching into Rohan – or the Rohirrim may have put down their Dunlending foes and seized settlements in Rhovanion. You may burn out the last nest of the Empire only to find that the Reunited Kingdom's recent victory over Adunabar has left them with a vast army bristling with steel – or the RK may be crippled by Tharbad's expansion into Arnor. Your victorious armies may not have time to consolidate their new lands before being put to the test by stronger and better-armed foes.
Playing as Far Harad allows you to see the results of the great drama that plays out over Middle-earth in your absence – and allows you to meddle in the unpredictable affairs of the north once you have secured your power in the south. Will you cast out the rich rulers of Umbar and replace them with your own dynasty, becoming the new threat to the Dunedain? Or will you secure peace with Elessar's heirs and pursue your own vendettas with the wild men who harass your borders in the East?
Establishing your place as more than a mere tributary to the Empire is the first step, but it is not the last challenge that awaits a Prince of Far Harad.
How big will this full map be? I assumed we would see the map go west and north to get the rest of the Lord of the Rings map but it sounds like the map edge may have to move east and/or south in order to fit in the extra factions so they are more than one territory wonders. While conquering the world as the RK in Wars of Men I came across a territory of "West Rhun" at the map edge. Will there be an "East Rhun" which we will be able to conquer as well or will it be assumed to exist but still be off the map edge?
The map is expanded in all directions in comparison to the one in TNS.