A nicely focused shockwave pattern meant to shatter a gate. then suddenly someone throws car battery into it, causing it to do more than it was supposed to, because the two relics involved had the same base material they affected. If you had not interfered like that, the gate would have been shattered, and that's it. Now the Kalesians will have to build a complete new wall section there after they finish taking the city.

The result of the two earth powers mixing was unpredictable, and thus it just can't easily be countered. You can't prepare completely for the wholly unpredictable.