One of the illustrious dynasties on Game of Thrones, the Targaryens in vain tried to bring their wrath to the kingdom of Dorne during Aegon's Conquest of Westeros. This War of Conquest is reported to be an upcoming Game of Thrones prequel, and it began in 2 BC when the dragonlord and his sister-wives, Visenya and Rhaenys landed at the mouth of the Blackwater.
With the spirit of Fire and Blood, the siblings conquered six of the Seven Kingdoms in two years' time. They were able to command the respect of Westerosi lords, and all but one ruling House, i.e. the Martells of Dorne. Westeros before the Conquest was divided into Seven independent but warring Kingdoms. The North was ruled by King Torrhen Stark, the Iron Islands and the Riverlands by King Harren Hoare, the Vale by Queen Regent Sharra Arryn, the Westerlands by King Loren I Lannister, the Reach by King Mern Gardener, the Stormlands by Argilac Durrandon, and Dorne by Princess Meria Martell.
Aegon lay waste to Harren Hoare's line and razed his supposedly impenetrable castle, Harrenhal. His general, Orys Baratheon slew the last Storm King, Argilac the Arrogant at the Last Storm, married his daughter, and founded House Baratheon. The Targaryens turned the King in the North, Torrhen Stark into the King Who Knelt. House Gardener was decimated, and Loren Lannister was stripped of his Kingdom in the Conquest's pivotal battle, Field of Fire. While Tyrells were given control of the Reach, Loren was made Warden of the West. After overtaking the existing kingdoms and forging them into a realm, the Targaryens failed to conquer Dorne. But why was the kingdom an exception in Aegon's expansionist war that took place approximately 300 years prior to the events of Game of Thrones?
Rhaenys Targaryen's Invasion
Aegon's Conquest boasts swift victories and bitter battles, but Dorne's saga doesn't fit in either of the two. It neither challenged Aegon nor did it kneel to his might and, in fact, the ruling House of the Kingdom - the Martells stayed true to their words, "Unbent, Unbowed, Unbroken." Aegon's youngest sister-wife, Rhaenys flew above the Prince's Pass (an overland route from the Reach and the Stormlands to Dorne) to seek the aging Princess Meria Martell's subjugation. A gateway into the deep sands of Dorne, the pass was guarded by Dornish spearmen.
Rhaenys avoided the overland route and instead flew over it on her mount, Meraxes. She eventually returned defeated, unable to unleash Fire and Blood (House Targaryen's words, and emphasized by Daenerys Targaryen on Game of Thrones) or engage the Dornish in a fight. Rhaenys flew to the abandoned castles of Vaith and Godsgrace and found only women and children at Planky Town. Finally, she found a stand-offish Meria Martell waiting at Sunspear. Meria made it clear that the Targaryens did not belong in Dorne and ordered her to return, while Rhaenys promised to be back with Fire and Blood.
Aegon, Rhaenys, Orys, and Harlan Tyrell invaded Dorne during the First Dornish War in 4 AC. Rhaenys seized the Dornish castles and torched Planky Town, but eventually, the dragons and fighters had no answer to Dornish guerrilla tactics. The Dornish refused to meet the Targaryens on battlefields but instead, retreated and often pelted them with rocks, arrows, and spears from above. Aegon foolishly claimed Dorne had fallen into his realm after finding Sunspear abandoned, leaving Jon Rosby and Harlan Tyrell in charge. Rosby was killed by Meria and Harlan and his army vanished while marching to Sunspear in 5 AC. Finally, in 10 AC, a bolt from the long-range artillery weapon, scorpion pieced Meraxes at Hellholt. The she-dragon plummeted to her death and destroyed Hellholt's higher tower. Though conflicting accounts exist about Rhaenys' death, fact remains that her body wasn't returned to King's Landing. The Kingdom of Dorne earned a reputation for being impregnable, something that King Joffrey Baratheon's hand, Tywin Lannister emphasized in Game of Thrones season 4.
Tywin (played by Charles Dance on Game of Thrones) offered Prince Oberyn Martell a place on the small council to appease him and to remind him of Dorne's importance in the fold. "In the East, the Targaryen girl has three dragons. Before long, she will turn her eyes towards Westeros. Only the Dornish managed to resist Aegon Targaryen and his dragons," Tywin rightly recalled. Rhaenys' grief consumed Aegon and Visenya, and they unleashed Fire and Blood on Dorne, burning every stronghold except Sunspear and its shadow city.
While many attributed this move to Aegon's fear of seeing Balerion meet the same fate as Meraxes, Archmaester Timotty says Sunspear wasn't attacked because Aegon wanted to divide and conquer the kingdom. The First Dornish War came to a halt in 13 AC when after Princess Meria's death, her son, Nymor sent his daughter Deria as a peace messenger to the royal court. She brought with her Meraxes' skull and a letter from Nymor declaring his intention of truce. Aegon read the letter atop the Iron Throne and thereafter flew to Dragonstone. He returned the next morning and signed a peace treaty with Nymor.
The Marriage That United Dorne With The Seven Kingdoms
Daeron I Targaryen's conquest of Dorne isn't as undignified as that of his ancestors. He vowed to rectify Aegon's mistake and took all possible cues from the First Dornish War. After fighting several gruesome battles, he managed to subjugate the Prince of Dorne and forty Dornish lords. While Daeron did technically become the first Targaryen king to conquer Dorne, he lost ten thousand men in taking it and tens of thousands trying to hold it down. The smallfolk still continued to resist and rebellion persisted. Daeron returned to Dorne in 160 AC and a year later, was killed in a truce negotiation. He was succeeded by Baelor the Blessed who not only pardoned his assassins but established harmonious relations with Dornish. After all, Dorne's expertise in guerrilla warfare compelled Tywin Lannister to appease Oberyn Martell (Pedro Pascal) in Game of Thrones.
Dorne remained independent due to an intersection of many factors, but primarily due to its unrelenting geography and the unwavering loyalty of its lords and the smallfolk. Moreover, most Kings and Westerosi lords met the Targaryens on battlefields, or in the case of Harren Hoare, threatened Aegon from his colossal fortification, Harrenhal, but the Dornish used elements of guerrilla warfare such as ambush and raids to bleed the conquerors. Dorne did join the Seven Kingdoms but peacefully through a marriage alliance. It was through Princess Daenerys Targaryen and Prince Maron Martell's marriage that the kingdom was brought into the fold. Later, a Targaryen, Emilia Clarke's Daenerys, would form an alliance with Ellaria Sand during her war for Westeros. Unfortunately, Cersei Lannister destroyed her allies one by one and she herself met a tragic end at the closing of Game of Thrones.