[Endoperez]

Ah, THAT was what I thought I was forgetting.

PD 11 is enough to catch spies. And as OG_Gleep mentioned, AI doesn't know the difference between 19 and 11. PD 19 is much more expensive than PD 11, and not that much more useful.

Some types of PD, like Ulm's Crossbowmen or Machaka's Archers, fare much better if you have few infantry units in the same province. It is probably worth it to line 4-8 infantry to the recruitment line for those nations.

You can recruit units even if you don't have the resources, BTW. The resources will accumulate over many turns, so 15-resource province CAN recruit 20-resource heavy infantry if given a few turns.