*Bob shakes head sadly*
"There is no apparent individual/self profit in dying to defend liberty..."
There! That's better. Many species produce individuals which sacrifice themselves for the good of the species as a whole. Humans are not removed from this calculus.
The individual may not be able to observe the long term aspects of the good that he has done, but he may be aware at the time that it is "the right thing to do."
Yes, we call them Heroes. The same brave effort expended to save only his own life makes him "stout-of-heart," and "determined," but it doesn't make him a hero. One expects a person to attempt to survive. What one does not expect is the individual who is willing to risk, or surrender, his(or her) life for the benefit of others. (Picture the drunken pilot in "Independence Day." He was in a position to recognize a unique opportunity to strike out in defense of his children, his nation, his world -- but at the cost of his own life. It didn't appear to take him long to decide. It seldom does.)