What do you call the collective singular as a rhetorical device? (e.g. 'the Hun')

I’m trying to figure out how to refer to the rhetorical device in which one refers to a collective as an individual member of that group, e.g. ’the Hun’ for soldiers of the German Empire during the first World War, or ’the Bantoo’ or ’the Hindoo’ in older ethnographic writing. An example, from the movie Patton:

'Now there’s another thing I want you to remember. I don’t want to get any messages saying that we are holding our position. We’re not holding anything. Let the Hun do that. We are advancing constantly and we’re not interested in holding onto anything except the enemy. We're going to hold onto him by the nose and we're going to kick him in the ass. We're going to kick the hell out of him all the time and we're gonna go through him like crap through a goose.’

The general is referring to German soldiers collectively, but through an imagined individual (perhaps because for military purposes, there's little point in differentiating among the individuals?).

It seems like this might be a subcategory of synecdoche.

Solution 1:

From the most general to the most specific (as italicized) of the rhetorical devices in your example that refer "to a collective as an individual member of" the collective:

In the rhetorical canon of invention, the topic of comparison includes devices of similarity and difference. One such device is analogy, a type of metaphor. Your example from Patton is a metaphor in the form of an extended analogy.

Patton (the character in the movie) draws out and extends a synecdochal metonymy to a point where it becomes metalepsis.

1. He uses a single German soldier, "the Hun" ('Hun' is an offensive term intended to demonize German soldiers as savages and barbarians), to stand in for "the enemy", that is, the entire German army. That single German soldier, called "the Hun", is then a synecdoche for all German soldiers.

synecdoche. A whole is represented by naming one of its parts (genus named for species), or vice versa (species named for genus).

(From Silva Rhetoricae.)

2. This synecdoche, representing the entire German army with a single German soldier, employs metonymy to refer the attribute of extraordinary cruelty, signified by the use of the offensive singular synecdochal term 'Hun', to all German soldiers--"the enemy".

metonymy. Reference to something or someone by naming one of its attributes.

(op. cit.)

3. Patton then extends the synecdochal metonymy into a metalepsis, by implying that "the Hun" (a term only remotely related to the German army) substitutes for "the enemy" (the German army) by way of the individual German soldier, who is held "by the nose", kicked "in the ass" and gone through "like crap through a goose".

metalepsis. Reference to something by means of another thing that is remotely related to it, either through a farfetched causal relationship, or through an implied intermediate substitution of terms. Often used for comic effect through its preposterous exaggeration. A metonymical substitution of one word for another which is itself figurative.

(op. cit.)