If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
The elves arrows are poised, the humans swords are drawn, and the centaurs lead the charge!
Left / Right Arrow Keys - Move.
Down Arrow Key - Stop.
Z or 1 - Shoot Arrows.
V or 4 - Summon Humans.
B or 5 - Summon Centaurs.