Leonidas I in the context of "Battle of Thermopylae"

The second Persian invasion of Greece (480–479 BC) occurred during the Greco-Persian Wars, as King Xerxes I of Persia sought to conquer all of Greece. The invasion was a direct, if delayed, response to the defeat of the first Persian invasion of Greece (492–490 BC) at the Battle of Marathon, which ended Darius I's attempts to subjugate Greece. After Darius's death, his son Xerxes spent several years planning for the second invasion, mustering an enormous army and navy. The Athenians and Spartans led the Greek resistance. About a tenth of the Greek city-states joined the 'Allied' effort; most remained neutral or submitted to Xerxes.

The invasion began in spring 480 BC, when the Persian army crossed the Hellespont and marched through Thrace and Macedon to Thessaly. The Persian advance was blocked at the pass of Thermopylae by a small Allied force under King Leonidas I of Sparta; simultaneously, the Persian fleet was blocked by an Allied fleet at the straits of Artemisium. At the famous Battle of Thermopylae, the Allied army held back the Persian army for three days, before they were outflanked by a mountain path and the Allied rearguard was trapped and annihilated. The Allied fleet had also withstood two days of Persian attacks at the Battle of Artemisium, but when news reached them of the disaster at Thermopylae, they withdrew to Salamis.

Leotychidas II (Ancient Greek: Λεωτυχίδας; Doric: Λατυχίδας Latychidas; c. 545 – c. 469 BC) was king of Sparta from 491–476 BC, alongside Cleomenes I and later Leonidas I and Pleistarchus. He led Spartan forces during the Persian Wars from 490–478 BC.

Born in Sparta around 545 BC, Leotychidas was a descendant of the Royal House of the Eurypontids (through Menamus, Agesilaus, Hippocratides, Leotychides, Anaxilaus, Archidamos, Anaxandridas I and Theopompus) and came to power in 491 BC with the help of the Agiad King Cleomenes I by challenging the legitimacy of the birth of Demaratus for the Eurypontid throne of Sparta. Later that year, he joined Cleomenes's second expedition to Aegina, where ten hostages were seized and given to Athens. However, after Cleomenes's death in 488 BC, Leotychidas was almost surrendered to Aegina.

The Agiad dynasty (Ancient Greek: Ἀγιάδαι, Agiádai) was one of the two royal families of the ancient Greek city-state of Sparta. They ruled jointly along with the Eurypontid dynasty, possibly from the 8th century BC onwards, being the senior of the two houses. The hypothetical founder of the dynasty was Agis I, possibly the first king of Sparta at the end of the 10th century BC, who subsequently gave his name to the dynasty. The two lines, who maintained an enduring rivalry, were, according to tradition, respectively descended from the twins Eurysthenes and Procles, both descendants of Heracles. The most famous member of the Agiad dynasty was Leonidas I, known for his heroic death at the Battle of Thermopylae in 480 BC. The last Agiad king was Agesipolis III, deposed by the Eurypontid Lycurgus in 215 BC.

Anaxandridas II (Ancient Greek: Ἀναξανδρίδας, meaning "descendant of Anaxander") was an Agiad king of Sparta from c. 560 BC to 524 BC, father of Leonidas I and grandfather of Pleistarchus. Under the leadership of the ephor Chilon, in office during the middle of the 6th century, Sparta ended its streak of violent conquests, such as in Messenia, and adopted a pro-Achaea policy based on diplomacy. Anaxandridas was succeeded by Cleomenes I.