A war picture isn’t something one imagines you taking on based on your previous work. Why did the genre captivate you?

Michod: I’d been wanting to make a war film for a while. Maybe it’s a continuation of my obsession with hermetically sealed bubbles of delusional men. [Laughs.] But I hadn’t been able to find my way in. I would have assumed once upon a time that it would have to be something dark and brutal and menacing. And then Dede and Jeremy [Gardner and Kleiner, Pitt’s producing partners at Plan B Entertainment] brought me the book. And that in was absurdity. I instantly saw a movie that would fit in the great tradition of American war comedy.

The word divisive has been tossed at “War Machine.” Do you think that’s fair?

Michod: This film is vehemently antiwar, so I get that people will think that. But I think it’s also politically ambiguous. These wars are not about parties — Afghanistan was started by Republicans and continued by Democrats and then picked up by whatever … this current administration is.

We have now wound down the wars of the 2000s and are somewhat more reluctant to jump into that kind of war with the likes of Islamic State. Do you think we’ve learned from the mistakes you document?

Michod: But we’ve been thinking about surging in Afghanistan again. And I don’t care who is in the White House but if that’s something we’re seriously contemplating, well, what is that going to achieve? Remember, the military is supposed to work for us.

Some of the criticism of “War Machine” has been about the message but some has also been about the fictionalization — McChrystal is really nothing like this in real life, but people watching it are obviously supposed to think it’s him. Did those liberties give you pause?

Michod: I made the decision early on to change character names early on because I wanted creative freedom and wiggle room. But I also did it because I wanted it to be about a larger war machine, not specific individuals.

But people think that what they’re watching is true since many of these characters are clearly based on real figures. Is that two-footing it?

Michod: I think all biopics are fiction; I never feel comfortable with the idea that I know exactly what a person is like or what their private conversations are like. So to be able to say from the outset [as an audience member] that “I know it will contain characters and events that seem familiar but it’s not to be taken as documentary fact” I think is good. It’s not dissimilar to what I did with “Animal Kingdom,” where it’s based very loosely on a criminal history in Melbourne but people understood — or hopefully understood — that it wasn’t an actual history. As long as you make clear these characters are your own invention I think it’s OK. It’s a lot more preferable to movies that purport to be true.

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There are people who will see this film and come away thinking “Michod is just opposed to war generally and that’s just unrealistic.” What do you say to them?

Michod: Humans have been fighting each other since they came out of the swamp. There’s no denying that wars will always be fought. But just because war is a fact of human civilization doesn’t mean we shouldn’t be questioning which we choose to fight and how we choose to fight them. The honorable thing we can do is say respect the troops and thank them for their service. But maybe the truly honorable thing is to hold them to account; when they talk about victory and doubling down missions they need to be able to explain what that victory looks like and how it can be achieved. Because you can’t just say you should spend trillions to justify the money and lives already spent.