Which sutras are most directly relevant to the virtue of courage? If I want to read through the origins of western (really, Greek) thought about the virtue we generally call courage, I know exactly where to go: Laches, Republic, Nicomachean Ethics, etc. Meanwhile, while courage has played a central role in many of the dharma talks I've listened to, if someone asked me where to look for a Buddhist theory of courage I wouldn't know any particular place to start. 

Within the most widely accepted Buddhist scriptures (especially but not limited to the Pali Canon) are there are any "go-to" sutras on the subject of courage? (Especially from a philosophical, psychological, or theoretical standpoint - whether or not that theory is grounded in narrative or discourse.)

This question gives several interesting references for modern writings about courage, but said I'm particularly interested in the older premodern stuff.
"Courage" isn't listed as one of the 37 factors.

So, wondering how "courage" is defined, I found this (non-Buddhist) definition on Wikipedia:


  Courage (also called bravery or valour) is the choice and willingness to confront agony, pain, danger, uncertainty, or intimidation. Physical courage is bravery in the face of physical pain, hardship, death or threat of death, while moral courage is the ability to act rightly in the face of popular opposition, shame, scandal, discouragement, or personal loss.


I guess two suttas I admire are (according to the above definitions):


"Physical" courage: Punna Sutta (SN 35.88)
"Moral" courage: Akkosa Sutta (SN 7.2)


And the Dhammapada is interesting too, some verses for example:


  
  Though one may conquer a thousand times a thousand men in battle, yet he indeed is the noblest victor who conquers himself.
  


and


  
  He who is friendly amidst the hostile, peaceful amidst the violent, and unattached amidst the attached — him do I call a holy man.
  




The essay Freedom From Fear suggests that "fear" is a mixture of other emotions:


  Think of a deer at night suddenly caught in a hunter's headlights. It's confused. Angry. It senses danger, and that it's weak in the face of the danger. It wants to escape. These five elements — confusion, aversion, a sense of danger, a sense of weakness, and a desire to escape — are present, to a greater or lesser extent, in every fear. The confusion and aversion are the unskillful elements. Even if the deer has many openings to escape from the hunter, its confusion and aversion might cause it to miss them.


Later it says ...


  The Canon lists these mental strengths at five: conviction, persistence, mindfulness, concentration, and discernment. 


... and tries to explains the role of each of these.

I think that "courage" isn't defined as a primary strength -- perhaps courageous acts are understood as being a consequence of other mental "strengths".



Do you feel confident in recommending any particular Jataka tales, re: a Buddhist view of courage? There are quite a few


There's one about the tigress and her cubs: the prince throws his body off a cliff to feed a hungry tigress, who would otherwise have eaten her own cubs. A moral aspect of that tale is that her eating her cubs would have been a grave "sin", a moral transgression -- it was that which he was saving the tigress from, I guess the moral being that ethics and compassion are more important than life.
Another is about the Bodhisattva as the captain of a ship. There's a pirate on board who's about to kill the other passengers, so the captain kills him. The moral aspect is that the other passengers were themselves Bodhisattva, killing them would have been a great sin, so the captain compassionately guarded the pirate from the terrible consequences which the pirate would have suffered as a result of killing Bodhisattvas.

That story is kind of famous because I think it's the only bit of Buddhist (or some might say pseudo-Buddhist) literature which appears to condone killing for some reason -- conversely for example see Getting the Message which includes ...


  When asked if there was anything whose killing he approved of, the Buddha answered that there was only one thing: anger. In no recorded instance did he approve of killing any living being at all. When one of his monks went to an executioner and told the man to kill his victims compassionately, with one blow, rather than torturing them, the Buddha expelled the monk from the Sangha, on the grounds that even the recommendation to kill compassionately is still a recommendation to kill — something he would never condone.


Anyway I think that the name of the captain in that story is "Captain Compassionate".