Ithilien
Ithilien was the region of Gondor that was west of the Anduin River from Osgilaith to Minas Ithil(Minas Morgul)
Ithil means the moon in Sindarin and Ithilien was the main region that Isildur ruled as Isildur founded Minas Ithil to rule over the Ithilien region.
Even the Tower of Cirith Ungol was built by Gondor as a fortress to watch over Mordor and defend Ithilien.
After Minas Ithil was captured by Sauron and the nazguls and became Minas Morgul. the Gondor forces of Ithilien tried their best to defend Ithilien from Sauron and Mordor.
However, Ithilien region fell into Sauron and the remnants of the Gondor forces of Ithilien would become the Rangers of the West that would be led by Faramir. Faramir would lead the Rangers of the West, the descendants of Ithilien to fight against the orcs, Haradrim and other forces of Sauron.
Pelargir
Pelargir was the main port city near the mouth of the Anduin River. During the War of the Ring, Pelargir was assaulted by the corsairs of Umbar, however Aragorn alongside Gimli and Legolas would relief Pelargir with the helpof the Dead Men of Dunharrow also known as the Oathbreakers(Army of the Dead in the movie).
In the original Lord of the Rings novel, Aragorn would release the Dead Men of Dunharrow for fulfilling their oath. The ships of the corsairs and pirates of Umbar was used to ship the troops of Southern Gondor to Minas Tirith.
Minas Tirith – Minas Anor and the White Tree of Gondor
Minas Tirith’s original name was Minas Anor where Anor means the Sun in Sindarin elf language. While Isildur would dwell in Minas Ithil, the Tower of the Moon, Anarion would dwell in Minas Anor the Tower of the Sun.
During the War of the Last Alliance of Elves and Men against Sauron, Anarion and Elendil both died in battle.
Isildur became the next heir of the High King of Arnor and Gondor and before Isildur headed to Arnor to claim the throne, he would plant the second White Tree of Gondor (there were many generations as they’ve constantly died off) at Minas Tirith. There was also a Palantir at Minas Anor.
Minas Tirith – Minas Anor- new capital of Gondor
Although, Minas Tirith was the hometown for Anarion, the bloodline of Anarion which was also the royal bloodline of Gondor would rule Gondor at Osgiliath.
However after the Great Plague and the Kinstrife of Gondor, the capital of Gondor was relocated from Osgiliath to Minas Anor(Minas Tirith).
After the nazguls sacked Minas Ithil and renamed it as Minas Morgul, the name of Minas Anor was changed to Minas Tirith.
The Minas Anor that meant Tower of the Sun would now be named Minas Tirith, the Tower of the Guard as determination to defend Gondor from the evil forces of Mordor. The Palantir of Minas Anor(Minas Tirith) would be sealed as the Palantir of Minas Ithil fell into the hands of the nazguls.
Minas Tirith – Ruling Stewards
After the mysterious missing of Earnur who was provoked by the taunt of the Witch King of Angmar, the bloodline of Anarion in Gondor was cut off and the reign of the Ruling Stewards began.
Before Aragorn, who was both the descendant of Isildur and Anarion returned to Gondor from the north, Gondor remained with no king.
The steward Ecthelion the First would build the White Tower at Minas Tirith, however the White Tree of Gondor would wither and until the return of Aragorn, the White Tree of Gondor didn’t stand above Minas Tirith as well.
Minas Tirith – Denethor the Second, War of the Rings
Aragorn would serve Thengel, the king of Rohan and the father of king Theoden and then Aragorn served Ecthelion Second the father of Denethor the Second under the alias of Thorongil.
Denethor Second was jealous of Thorongil and possibly even sensed that he was the rightful king and heir of Gondor.
Denethor Second also despised Gandalf over his jealousy despite Denethor Second being a fair and good ruling steward during his early reign.
Denethor Second would eventually put his hands on the sealed Palantir to seek power. However the Palantirs were already corrupted by Sauron as Sauron corrupted the Palantir of Minas Morgul that was once the Palantir of Minas Ithil.
Sauron would corrupt both Saruman and Denethor the Second by the Palantir. Denethor Second would become insane and started to make irrational decisions that shook the fate of Gondor and allies such as Rohan.
Minas Tirith – Last Hope of Gondor
Still, Minas Tirith with its Mithril Front Gate and the castle walls forged by the impeccable masonry of Numenor would stand as the final and possibly the only fortress to stand against Sauron and the forces of Mordor.
In the movie, siege weapons were able to destroy the stone walls of Minas Tirith but in the original novel, it was impossible to take down the masonry of Numenor.
Gandalf would find the Scroll of Isildur at the archives of Minas Tirith that helped him identify the One Ring. Also, Minas Tirith would stand as Gondor’s final defense against Sauron and Sauron would launch a full-scale assault with the Easterlings and the elite forces of Minas Morgul to destroy Minas Tirith.
Pelennor Fields and Rammas Echor
The Pelennor Fields were the prosperous plains in front of Minas Tirith next to the Anduin River. The stone walls of Rammas Echor would guard the Pelennor Fields and the Gondor people would thrive in the fertile plains of Pelennor.
In the movie, Lord of the Rings, Pelennor Field was an empty bare land, however in the original novel Lord of the Rings the Pelennor Field was full of inhabitants as it was very fertile lands and the Pelennor Field was the crucial food source for Minas Tirith.
Under the command of the Witch King of Angmar, the walls of Rammas Echor and the Pelennor Fields were overrun and the siege of Minas Tirith takes place.
The Pelennor Fields would become the final battle ground for the clash of the Rohirrim led by Theoden, orcs of Minas Morgul, Witch King of Angmar, oliphaunts of Harad, forces of Gondor etc. (Dead men of Dunharrow only for the movie as well). The Witch King of Angmar and Theoden would die at the Battle of the Pelennor Fields.