Question

In a modern poem, the writer makes a passing reference to the siege of Stalingrad in WWII. This is an example of:

Answer 1

just from the question I would say allusion- an expression designed to call something to mind without mentioning it explicitly; an indirect or passing reference.

Answer 2

dont forget to give me best answer if this is right please

Answer 3

I agree with @mkerr017, its an allusion