Event: Euron Greyjoy - Victorious Battle (Political Wins)

Episode 3: The Queen's Justice at 55:21
As the Unsullied are busy attacking Casterly Rock, Euron's Iron Fleet ambushes their ships, destroying the Unsullied navy and cutting off any sea-based escape route in the process.

Jaime Lannister to Olenna Tyrell: "They won't be able to hold it (Casterly Rock). Euron Greyjoy's navy burned their ships, we emptied the larders before we left. Eventually, they'll be forced to abandon their position and march all the way across Westeros."
(Victorious Battle)