The correct interpretation that the poet's description of his aunt supports is:
The poet feels that the public perception of the war is inaccurate and that the reality is much different.
This interpretation is backed by the phrase "my sweet old etcetera," which implies a sense of irony or dismissal of the grand narratives or justifications often associated with war. The mention of the aunt's perspective suggests a contrast between what individuals like her may believe about the war and the more complex, perhaps less romanticized, reality of it.