Battle of the Goldroad

The Third Battle of Tumbleton is an engagement in Daenerys Targaryen's invasion of Westeros, in which Daenerys Targaryen's Dothraki horde engaged the main House Lannister field army as it was returning east to King's Landing after successfully sacking Highgarden. It was the first time that Daenerys committed one of her powerful dragons to battle, personally riding her mount Drogon into combat.

Prelude
Tumbleton is a natural choke point for any army advancing up the Roseroad from Highgarden in the southwest to King's Landing in the northeast - located in the northeastern corner of The Reach, amidst hills and cliffs around the source of the Mander River. While the Mander flows southwest, a short distance farther east is the Blackwater Rush, which itself flows east to the sea, with King's Landing at its mouth. The Roseroad passes Tumbleton to the south, almost reaching the sea, until it reaches the southern bank of the Blackwater's mouth - at which point an army needs to cross the river to reach King's Landing on the northern side.

Due to its strategic location, the last major hurdle for an army heading east on the Roseroad to King's Landing, Tumbleton has thus seen a number of major battles throughout history, notably the first and second battles of Tumbleton, which were fought during the Dance of the Dragons - and both of which involved dragons burning out entire armies.

After the Fall of Highgarden, the bulk of the remaining Lannister army advanced east led by Jaime Lannister, along with Randyll Tarly commanding his own Houses's formidable forces.

In the books
In the A Song of Ice and Fire novels by George R.R. Martin, an equivalent battle has not occurred. The TV show has surpassed the timeline of the books, so it is unclear if an equivalent battle will occur or not.