But I want to write a bit about the opiates in the American Civil War (1961-1865). What I found when I search a bit.
Apparently opiates were used by the kilo during the 19th century. Physicians were dazzled by the effectiveness in case just about anything. In the Civil War they gave opiates for:
diarrhea and dysentery, opiates relieved cramps and had a constipating effect
cough suppressants for patients with pneumonia, pleurisy, asthma, bronchitis, influenza, and tuberculosis
pain relief for patients with wounds and injuries, [...] stomachaches, headaches, gallstones, hemorrhoids, tetanus, typhoid fever, malaria, syphilis, and neuralgia.
restlessness, delirium tremens, insanity, and depression
So anything really a soldier could suffer from. It is noted however it has sedative effect, so I doubt they got much before battles. Albeit in some cases poor performance of generals could be explained by opiate addiction.
It is also known that Union physicians gave almost 10 million opium pills, and 3 million ounces of other opiates, with 30 thousand ounces of morphine to the soldiers. The Union mobilized over 2 million troops.
It is unknown how much the Confederates gave, but calculating with similar ratio, for their 1 million soldier, this amount should be about half the above numbers.
Since there were so many things to use it for, I have to assume that all soldiers got something at least once. But addiction only grew from repeated use within short time frame. Which means for that the most susceptible were the wounded, especially the maimed.
I wonder about other drug use in the same war.

Here's two from the top research hits:
https://library.medicine.yale.edu/blog/great-risk-opium-eating-how-civil-war-era-doctors-reacted-prescription-opioid-addiction
https://www.smithsonianmag.com/history/inside-story-americas-19th-century-opiate-addiction-180967673/
Plus the book I found some data.