This question is partially open ended.
I'm looking for a Latin idiom or euphemism or phrase that expresses something being from or related to practice as opposed to being related to theory. Something that was practiced or developed or is otherwise related to being "in combat" as opposed to "on paper". Surely the Romans had a distinction for this with their love of heuristic and difficult numbering system.
I'm not asking for a translation for "in combat" or any host of English phrases that suit this purpose, or anything specific, I'm wondering if there is a more general Latin expression for this.
This seems like something that we surely have inherited a Latin phrase for in modern speaking like "Sine qua non" or "Cui bono". Does this phrase exist in the modern lexicon of adopted Latin expressions? If it's not something that exists in the aforementioned, what would or could it be?
The way I would like to use this Latinism would fit well into the sentence:
"Our tactics were tested and refined in the field after we implemented them in training exercises"