immediate consequences of the battle
Within the course of the battle an important consequence was the death of over 20,000 invading soldiers. But as the battle, it is the Greeks who remained behind as a rear-guard whose actions were most consequential in the immediacy of the battle and following circumstance.
When Leonidas of Sparta discovered they were being out-maneuvered he dismissed the majority of the 7000 man strong Greek force. He stayed behind with his 300 Spartans along with 700 Thespians (who volunteered to remain and fight in spite of certain demise), 400 Thebans as hostages and a small assortment of volunteers from other city-states.
As mentioned briefly earlier, the fact that these 1,500 Greeks remained at their base to fight the oncoming wave of Hydarnes' Immortals is what allowed thousands of other Greek soldiers from the battle to retreat successfully.
When Leonidas of Sparta discovered they were being out-maneuvered he dismissed the majority of the 7000 man strong Greek force. He stayed behind with his 300 Spartans along with 700 Thespians (who volunteered to remain and fight in spite of certain demise), 400 Thebans as hostages and a small assortment of volunteers from other city-states.
As mentioned briefly earlier, the fact that these 1,500 Greeks remained at their base to fight the oncoming wave of Hydarnes' Immortals is what allowed thousands of other Greek soldiers from the battle to retreat successfully.
To conclude, in the words of Victor Hanson:
"So almost immediately, contemporary Greeks saw Thermopylae as a critical moral and culture lesson. In universal terms, a small, free people had willingly outfought huge numbers of imperial subjects who advanced under the lash. More specifically, the Western idea that soldiers themselves decide where, how, and against whom they will fight was contrasted against the Eastern notion of despotism and monarchy — freedom proving the stronger idea as the more courageous fighting of the Greeks at Thermopylae, and their later victories at Salamis and Plataea attested."
"So almost immediately, contemporary Greeks saw Thermopylae as a critical moral and culture lesson. In universal terms, a small, free people had willingly outfought huge numbers of imperial subjects who advanced under the lash. More specifically, the Western idea that soldiers themselves decide where, how, and against whom they will fight was contrasted against the Eastern notion of despotism and monarchy — freedom proving the stronger idea as the more courageous fighting of the Greeks at Thermopylae, and their later victories at Salamis and Plataea attested."