If you recall the movie 300, it immortalizes in film—in a very, very graphic way–the battle of Thermopylae when the Persian army led by Xerxes sailed across the Aegean Sea in order to invade Greece and conquer the Greek city-states.
Well there was a force led by the Spartan general Leonidas and armies from various Spartan city-states that come together to defend a very small pass that the Persian army had to get through. If you remember in the movie, and actually in history as commemorated by the Greek historian Thucydides, these Spartans fought to the bitter end.
With high esprit de corps they gave their life for Greece.
So what does it take to have that kind of esprit de corps?
First you need to know that you can count on the person to your left and to your right with a high level of trust.
Second of all you need a clear idea of where you fit in the organization. The organization needs to have a set of values, a vision, and a purpose that touches you deeply inside. That causes you then to want to commit to it.
So you have the people to your left to your right that you know you can count on and you have this tremendous vision and purpose that that helps fulfill you as a human being and helps give your life purpose.
Those are those are two ways to build esprit de corps.