I don't see any enemy units either, but what I had more trouble with was that I don't see myself making any progress - there doesn't seem to be any indication of mine or the enemy's health (unless that red number 50 means something?) and my units just disappear when they reach the enemy castle.
Also, the units I can buy have no description of their purpose, the only difference I can see besides the cost is one point of health? And there is no indication of how to scroll around the battle map, I only discovered by accident that you have to move the cursor to the edges of the screen.
Sorry to be critical, but I don't think this game is developed far enough to be called a beta yet. With more work it might be pretty good but there is no motivation for me to play as it currently stands.