What Is Thermopylae? Halo Season 2’s Spartan Reference Explained

Spoilers are ahead for Halo season 2, episode 6, “Onyx.”

Throughout the Halo TV show’s sophomore outing, various characters bring up the term “Thermopylae.” During a key moment in the Fall of Reach episode, Master Chief (Pablo Schreiber) mentions Thermopylae to Admiral Jacob Keyes (Danny Sapani) — an apparent reference to the evacuation ship that acts as the Pillar of Autumn‘s TV series stand-in. However, that’s not the last time Thermopylae is mentioned. In Halo season 2, episode 6, “Onyx,” ex-Spartan-turned-rebel-pirate Soren-066 (Bokeem Woodbine) mentions the term to his wife, Laera (Fiona O’Shaughnessy), while they search the titular planet.

Even though the Halo TV series takes place in the Silver Timeline — an alternate version of events that’s separate from the core canon of the video games and books — it’s still heavily influenced by other entries in the franchise. The sophomore outing in particular has taken great pains to reference small details from the Halo games or put creative spins on pre-existing characters, like Halsey’s replacement James Ackerson (Joseph Morgan). Perhaps unsurprisingly, the term “Thermopylae” also crops up in the core Halo canon, though the reference is much more loaded than viewers might realize.

Soren Mentions Thermopylae While Looking For Kessler On Onyx

In the fifth episode of the Paramount+ series’ sophomore installment, Soren and Laera spend the bulk of their time searching for their son, Kessler (Tylan Bailey). After Soren’s vengeful desire to find Dr. Catherine Halsey (Natascha McElhone) lured him into a trap set by Ackerson and ONI, Laera realized that she and Kessler needed to leave Halo‘s The Rubble. While trying to escape with rebel Kwan Ha (Yerin Ha) on Soren’s ship, the mother-son duo run into a roadblock: Soren’s mutinous crew. In order to save Laera’s life, Kwan is forced to temporarily abandon Kessler.

After Laera and Kwan save Soren and the other Fall of Reach survivors, they regroup on Aleria. Soren and Laera eventually learn that Kessler isn’t on Aleria at all; he was taken by the UNSC. So far, Halo hasn’t been explicit about why the UNSC took Kessler, but it’s likely due to his supposedly sterile Spartan father. On the UNSC- and ONI-controlled Onyx, Dr. Halsey gives Soren and Laera some indication of where Kessler might be held. As the desperate parents search the planet, they come across a UNSC installation, prompting Soren to mention Thermopylae.

The Halo Series Features A Ship Class Called Thermopylae

During the Fall of Reach, Corporal Talia Perez (Cristina Rodlo) worked with the late Admiral Keyes to evacuate the civilian survivors. Meanwhile, the Chief and Keyes’ forces held the Covenant invasion off. Before the Covenant glassed the planet, Keyes sacrificed himself to ensure Perez’s escape, making him one of the key characters who dies in Halo season 2, episode 4. Thanks to Keyes’ efforts, Perez is able to pilot the ship off-world. Earlier, Master Chief seemed to indicate that the evac ship was called Thermopylae — a line that fits well with Soren’s in episode 6.

Viewers know that the Thermopylae, piloted by Perez, made it to Onyx. The corporal has even joined the ranks of Ackerson’s Spartan-III program. It seems Soren must have recognized the ship, and realized that the UNSC and ONI relocated Reach’s survivors to Onyx — a planet with a secret Forerunner connection. In Halo‘s core canon, the Thermopylae-class supercarrier is a durable, powerful ship that was built in response to the Covenant’s impressive capital ships. In Halo: Evolutions, the UNSC Thermopylae destroyer features in the Battle of 18 Scorpii (via Halopedia).

Thermopylae Is A Reference To The Historic Spartan Battle In Ancient Greece

The name of Halo‘s ship is a reference to the Battle of Thermopylae, which was fought in 480 BC. The conflict saw the Achaemenid Persian Empire, led by Xerxes I, and an alliance of Greek city-states led by Sparta’s Leonidas I, clashing in a three-day battle. One of the most prominent battles in the Persian invasion of Greece, the Battle of Thermopylae occurred nearly a decade after another historical conflict — the Battle of Marathon. At Marathon, Greek forces were able to repel the Persian invasion, but Thermopylae was all about noble sacrifice (via Livius.org).

Vastly outnumbered, the Greek forces displayed one of history’s most famous last stands. In pop culture, the Battle of Thermopylae served as the inspiration for 300. The landmark battle endures as a story because it illustrates the passion even the most disadvantaged soldiers have when it comes to defending their homeland. Given Halo‘s use of the Spartan moniker, it makes sense that the franchise would include other historical references, and the use of Thermopylae as an evacuation ship — its own kind of last stand on Reach — reiterates the show’s attention to detail.

Sources: Halopedia, Livius.org