Inland Route
Bob looked at the map and pointed well inland of any of the major routes.
"What if we don't ambush any of them, but instead, we zigzag across the pattern, as if we were a wandering monster pack being chased from place to place. It would confuse them with its disorganized nature, and it would let us search their territory to see if there are any signs of where they might be making the new clones.
I suspect that it is actually in the city, where we won't be able to easily get to the next summoning spell, but if it is still out in the wild, then there is a chance that we can break their reinforcements a little more, and not just by killing them in vast quantities.