Unsure where to put this, so mods please put this topic in right board, if its misplaced

Im playing as Parthia at the moment, and had just defeated Pontus (strange btw, the only had Bithynia left, and 3 Eastern Infantry and they demanded 5600 denarii for ceasefire). Then I got in war with Greeks (Horse Archers VS Hoplites...slaughter) and this thing happened:

Hoplites staring at stone

Anyone else seen it?