The excellent Guy Clark has a song called "Soldier's Joy, 1864" on his 2002 album The Dark, crediting its composition to himself & Shawn Camp.

The lyrics describe a US Civil War soldier needing something to kill the pain of having his wounded leg amputated in a field hospital and then becoming an addict. Key lines include:

"He handed me a bottle, said 'Son drink deep as you can',
He turned away then he turned right back with a hacksaw in his hand.'

And later:

"Gimme some of that Soldier's Joy, you know what I crave,
I'll be hittin' that Soldier's Joy till I'm in my grave."

It's pretty clear from the context that he's talking about a solution of morphine.