Summary

300: Rise Of An Empire begins around 490 BCE and ends in 480 BCE, showing some major battles of the Greco-Persian War.
The timeline of Rise Of An Empire is clear, but its ties to 300 are confusing, as it spans events before, during, and after 300.
The bulk of Rise Of An Empire occurs during 300, but the final battle, Salamis, happens afterward, showcasing a turning point in the war.

Rise of an Empire did feature some returning characters. Despite its unorthodox nature as far as sequels go, Rise of an Empire does connect quite well to 300. That connection isn't always very clear, though, especially as far as the duology's timeline is concerned.

300: Rise of an Empire deals with the same general time period of history that 300 does, namely the Greco-Persian War. Rise of an Empire features the Battles of Artemisium and Salamis, and briefly the Battle of Marathon, while 300 focuses on the Battle of Thermopylae. Those battles took place over a fairly large amount of time in real life, and the movies cover a large portion of the Greco-Persian War, which makes it hard to place exactly when Rise of an Empire takes place in relation to 300 without some historical context.

Themistocles from 300 Rise of an Empire standing in front of a red background

What Happened To Themistocles In 300: Rise Of An Empire

The ancient Greek soldier Themistocles was depicted in the 2014 film 300: Rise of an Empire, but some liberties were taken with history in the movie.

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300: Rise Of An Empire Begins Around 490 BC & Ends After 480 BC

The first scenes of Rise of an Empire depict the Battle of Marathon, and particularly Themistocles' involvement in it. While the movie took some creative liberties with its historical accuracy, as Themistocles didn't kill Darius I, it does match up with when the Battle of Marathon took place in real life, according to Encyclopedia Britannica: 490 BCE. That battle marked the end of Darius I's invasion of Greece, and Xerxes I wouldn't begin his invasion until 480 BCE. That year is also when the main battles of Rise of an Empire, Artemisium and Salamis, took place, as well as the battle featured in 300, Thermopylae.

300: Rise of an Empire Timeline
Battle	Year
Marathon	490 BCE
Artemisium	480 BCE
Salamis	September 480 BCE

300: Rise Of An Empire Takes Place Before, During & After 300's Timeline

The timeline of Rise of an Empire is fairly clear, but the way it fits with 300 is not. Rise of an Empire takes place before, during, and after the events of 300 at different points in the movie, which is a major source of the confusion. The Battle of Marathon takes place 10 years before all of 300 and most of Rise of an Empire. The Battle of Artemisium and the Battle of Thermopylae took place at the same time, as they were planned as a simultaneous defensive strategy where the Spartans would defend by land while the Greek fleet defended by sea.

The Battle of Artemisium makes up the bulk of Rise of an Empire, so most of the movie took place at the same time as 300. However, the final battle of Rise of an Empire, the Battle of Salamis, took place after 300 and a few months after Artemisium and Thermopylae. Because of the battles in Rise of an Empire, it and 300 depict a significant portion of Persia's two invasions of Greece. Xerxes' invasion would last another year, but Salamis was a major turning point in the Greco-Persian War. Together, 300 and 300: Rise of an Empire fill out their timelines quite well.

Source: Encyclopedia Britannica