300 Rise of an Empire movie is based on Frank Miller's latest graphic novel Xerxes, and told in the breathtaking visual style of the blockbuster "300," this new chapter of the epic saga takes the action to a fresh battlefield-on the sea-as Greek general Themistokles attempts to unite all of Greece by leading the charge that will change the course of the war.
Queen Gorgo (Lena Headey) tells her men about the Battle of Marathon, in which King Darius I (Yigal Naor) of Persia was killed by General Themistocles (Sullivan Stapleton) of Athens. Darius' son, Xerxes (Rodrigo Santoro), witnesses his father's death, and is advised to not continue the war, since "only the gods could defeat the Greeks".
Darius' naval commander, Artemisia (Eva Green), claims that Darius' last words were in fact a challenge and sends Xerxes on a journey through the desert. Xerxes finally reaches a cave and bathes in an otherworldly liquid, emerging as the "God-King". He returns to Persia and declares war on Greece.
As Xerxes' forces advance towards Thermopylae, Themistocles meets with the council and convinces them to provide him with a fleet to engage the Persians at sea. Themistocles then travels to Sparta to ask King Leonidas for help, but is informed by Dilios (David Wenham) that Leonidas is consulting the Oracle, and Gorgo is reluctant to side with the Greeks.
Themistocles later reunites with his old friend Scyllas (Callan Mulvey), who infiltrated the Persian troops and learned Artemisia was born Greek, but defected to Persia after Greek soldiers killed her parents and raped her when she was a child. She earned her place as a naval commander by brutally killing several of Darius' enemies.
Themistocles leads his men, which include Scyllas, Scyllas' son Calisto (Jack O'Connell) and Themistocles' right-hand man Aesyklos (Hans Matheson) to the Aegean Sea. They ram their ships into the Persian ships and charge them, slaughtering several soldiers before retreating.
The following day, the Greeks force one of the Persian ships into a crevice, where it becomes struck, and charge the other ships, killing more Persians. Impressed with Themistocles' skills, Artemisia has him brought onto her ship, where they have sex. She offers him a place in her army, but he refuses, causing her to swear revenge.
The Persians spill tar into the sea and send soldiers with bombs to infiltrate the Greek ships. Artemisia and her men fire flaming arrows and torches to ignite the tar, but Themistocles manages to kill one of the soldiers, who falls into the tar carrying a torch, causing ships from both sides to explode.
Themistocles is thrown into the sea by an explosion and nearly drowns before being rescued by Calisto, and stands by Scyllas' side as he succumbs to his injuries. Believing Themistocles to be dead, Artemisia and her forces retreat.
Themistocles learns that Leonidas and the 300 have been killed by Xerxes and returns to Athens to confront Ephialtes (Andrew Tiernan), the Spartan traitor, who reveals that Xerxes plans to attack Athens, and is regretful of his actions, welcoming death. Themistocles spares him instead, so he can warn Xerxes that the Greek forces are gathering at Salamis, and then visits Gorgo in Sparta while she is mourning Leonidas to ask for her help, but she is too overcome with grief.
In Athens, Xerxes' army is laying waste when Ephialtes arrives to deliver Themistocles' message. Upon learning he is alive, Artemisia leaves to ready her troops for battle, against Xerxes' wishes. The Greek ships crash into the Persians ships, and the two armies battle, beginning the decisive Battle of Salamis. Themistocles and Artemisia fight, and Themistocles overpowers her.
Gorgo had been narrating the tale to her army, and leads them to assist in the battle alongside other allied armies, outnumbering the Persians. Themistocles urges Artemisia to surrender, but she tries to kill him and is stabbed through the stomach. With her dying breath, she sees Xerxes turning his back on her as he retreats. Themistocles and Gorgo vow to follow him into the final battle.