Shit has many uses in Army language, but is way more specific than Fuck--which is used for everything. In Iraq, I washed a load of clothes and dumped the unfolded load of laundry on my bunk. Someone asked if I was going to chow. I said, "I have get my shit off the bed first."
In the Army, shit is can be a substitute for every other noun--up to a certain size.
If something can fit on a bunk, like laundry or field gear, you can say, "That's my shit." But when referring to his Humvee, the driver says, "That bitch is mine." When I first got to Iraq, the parking lot where we were pitching a maintenance tent had to be cleaned. The sergeant in charge said, "We have to police this bitch up."
Shit also has other uses. Shit can actually refer to feces as when someone leaves a room to "take a shit." That is an interesting linguistic twist in itself. What the speaker will be doing in fact (one hopes) is leaving the shit behind, but since effort is involved, taking is the verb--the same usage as taking a picture. Another twist is in the use of the s-word as an exclamation. "Shit!" is generally negative, but "No Shit!" is positive. If I tell Private Snuffy he has guard duty he will exclaim, "Shit!" to express his dismay. If later on I tell him the Private Duffy has duty in his place, Snuffy will say, "No Shit!" and be happy.
But the main use is as a pronoun. Looking at someone else's food, I might say, "I don't like that shit." If my tools were in disarray I would say, "I need to get my shit together." If someone else were advising me to put my tools in order they might use the same phrase or the odder form, "Get your shit straight!" You can't think literally in most uses of shit.
By now you must have had "enough of this shit" so I will "stop this shit" right now. Except to add that the most common modifier of the word of the day is Bull, often said as if it had three syllables.
