A somewhat flawed grid, but not uninteresting.

The "Korean" and "Paris" categories work, I think.

The remaining two ... well, not so much. I can see your logic after the fact, but the cities in question could be grouped in several different ways (especially given the large number of conflicts throughout history) and I don't think you can reasonably expect people to arrive at the solution you were looking for without a bit of blind luck.

The "Rome" group in particular feels weak to me. The expression you were looking for is not nearly unique enough -- surely it can be applied to all of the cities in the "Baltimore" group as well (and countless other places too)?

Still, your grid prompted me to look up a few things and learn a bit about history, so thanks for that! :-)