Courage

Meet Siegfried Loraine Sassoon. Taken circa May, 1915 when he was twenty-eight years old and with all of nine months-ish in the army, much of that time having been spent in the hospital.

We see him above as a newly-minted 2nd Lt. in the Royal Welsh Fusileers headed off to France. Sassoon had all the earmarks of a rich douchebag. He came from money and was well-educated but did little but hunt foxes and write sappy poetry. But when the twentieth century began in August, 1914, Siegfried  joined up - as an enlisted man.
He was on the fast track to becoming just another nameless bullet magnet across the channel until his plan was thwarted by a riding mishap during his training. He recovered just in time for the "Oh shit!" reality of the war to have begun to dawn on folks. 
So here's Sassoon: He fell of a horse as a private but got well as an officer and an infantry platoon leader at that. 
He took to it, seemingly.
He had some sort of manic courage that led his platoon to call him "Mad Jack" and only felt confident when he was with them.
But he could wax random.
He once, under the covering fire of a few rifles, routed  sixty or so German defenders from a trench on the Hindenburg Line with the understanding that when the trench was secure he'd tell the lads to come up.
A tense hour and a half later, his platoon finally crept close only to find Sassoon kicked back in the German trench - reading.
However, another time: On 27 July 1916 he was awarded the Military Cross; the citation read:

"2nd Lt. Siegfried Lorraine [sic] Sassoon, 3rd (attd. 1st) Bn., R. W. Fus.

For conspicuous gallantry during a raid on the enemy's trenches. He remained for 1½ hours under rifle and bomb fire collecting and bringing in our wounded. Owing to his courage and determination all the killed and wounded were brought in."

To my mind what makes him a hero is what happened a century ago yesterday.
Sassoon wrote his letter, "Finished with the war. A soldier's declaration."
It was published in Bradford Pioneer on July 27 and read to the British House of Commons on July 30, 1917. It was printed in the London Times the following day. 

"Lt. Siegfried Sassoon.

3rd Batt: Royal Welsh Fusiliers.

July, 1917."

"I am making this statement as an act of wilful defiance of military authority because I believe that the war is being deliberately prolonged by those who have the power to end it. I am a soldier, convinced that I am acting on behalf of soldiers. I believe that the war upon which I entered as a war of defence and liberation has now become a war of agression and conquest. I believe that the purposes for which I and my fellow soldiers entered upon this war should have been so clearly stated as to have made it impossible to change them and that had this been done the objects which actuated us would now be attainable by negotiation.

I have seen and endured the sufferings of the troops and I can no longer be a party to prolong these sufferings for ends which I believe to be evil and unjust. I am not protesting against the conduct of the war, but against the political errors and insincerities for which the fighting men are being sacrificed.

On behalf of those who are suffering now, I make this protest against the deception which is being practised upon them; also I believe it may help to destroy the callous complacency with which the majority of those at home regard the continuance of agonies which they do not share and which they have not enough imagination to realize"

This is treading one's Oscar Meyer in a most public and dangerous way.
To prevent his being court-martialed, his buddy, Robert Graves, convinced the powers that Siegfried had simply gone off his nut.
They bought it so he was sent to Craiglockhart Hospital in Edinburgh to be treated or "shell shock".
He wasn't crazy but he wasn't well either. He copped to seeing dead members of his platoon crawling across the floor of his room at night and apparently once, while on leave in London, he'd had to step over rotting corpses in Piccadilly Circus.
In the end he voluntarily went back to France to rejoin his men.
Courage

"Suicide in the Trenches"

Siegfried Sassoon

I knew a simple soldier boy

Who grinned at life in empty joy,

Slept soundly through the lonesome dark,

And whistled early with the lark.

In winter trenches, cowed and glum,

With crumps and lice and lack of rum,

He put a bullet through his brain.

No one spoke of him again.

You smug-faced crowds with kindling eye

Who cheer when soldier lads march by,

Sneak home and pray you'll never know

The hell where youth and laughter go.