[Zurai]

Depends entirely on things mentioned earlier, like what race you're playing and what size map, etc. 20 province defense as Jotunheim is about 50x more effective than 20 province defense as Machaka or C'tis. I rarely even bother with PD as those two nations because their militia has LOUSY morale and tends to rout in entirety at the drop of a hat. 20 PD as Jotuns is effective enough to stave off small to medium sized armies and most distance attack spells until the very late game.