We see in the movie 300 of completely fearless men that would gladly die for Sparta. They showed the soldiers’ harsh training since they were children.
Are these things historically accurate?
Are there historical records of their military training regimen?
The movie 300 is based on what's called the "Spartan mirage" - the myth of what Sparta was supposedly like. The origin of this myth is Spartan propaganda and the idealised stories told by foreign visitors. I've written many posts on how the reality was quite different, which you can find in my profile here. Specifically, you might be interested in the threads Is the military worship of the Spartans really justified? and How did the Spartans train? as well as How accurate is the movie "300"?