Do history departments across many US colleges regularly conflict with political science/IR departments?

I ask out of curiosity based on my own experience, and I mean it lightheartedly! Just finished my undergrad and one particular thing that stuck out to me as a polisci (technically diplomatic studies but its the same departme---whatever that's not important anymore) guy who enjoyed taking history courses was the level of enmity the history department had for the polisci department and vice versa. Graduate-student thesis defense panels would include professors from both, and from what I gathered these would be testy situations when one student in one department had to defend mostly to a prof from the other (even though the panelists from the same department would likely know the student and have helped on their work).

It WAS slightly uncomfortable to hear a history professor go on a tirade against polisci undergrads when I thought I'd been doing a pretty good job absorbing the material of the course (he wouldnt have known my major and I got an A so I doubt he was speaking specifically to me, but the sentiment remains). So I'm curious if there's a more in-depth reason for this inter-departmental competition? I feel like the two disciplines are pretty much inseparable for someone who wants to take their studies seriously: one feels prone to polemics without the other.

I have a very specific question about the terminology used in history as an academic discipline. Occasionally I see reference to "articles", meaning published, peer reviewed work. Is this the common term? In computer science, with which I am more familiar, "paper" is universally used.

I've got a question about what I think fits: How do historians decide when to address a certain event or series of events "genocide" and when to not?

Two examples come to mind specifically, one is Cambodian genocide and the other, Holodomor or the Great Purges. In these examples, what strikes me as different is the fact that (at least some of) the perpetrators were essentially of the same racial/ethnic/religious/cultural background as the victims, and – strikingly different from the Holocaust or Armenian genocide or Rwanda genocide – it doesn't seem that the point of the perpetrators was to completely eliminate some racial/ethnic/religious/cultural group.

What authors who have books in English, whether originally in English or translated, would you recommend for the study of political realism throughout history other than the following (whom I've already read):

• Aristotle

• Thucydides

• Hobbes

• Machiavelli

• Clausewitz

• Sun Tzu

• Waltz/Jervis/Gilpin/Walt/Mearsheimer (modern day authors)