Question

What does Anchises describe as the "Romans' art"?

Answer 1

Here is how Anchises describes roman's art:
To pacify, to impose the rule of law,
To spare the conquered, battle down the proud.

I believe what he described as roman art is its military might / the ability to conquest. He is a patriotic writer that had a deep love to his country and what it stands or and it always reflected in his writing.