It's fun and intense (combined with the music and marching sound of the troops). The art style is nice, it feels cohesive and makes me feel like my empire is at war with a formidable enemy (and they did beat me, eventually).
Using the slider to send the amount of troops can be tricky, especially if you want to send a specific amount under countdown time pressure. Maybe adding a +1/-1 and +10/-10 buttons could make it easier for players to control the amount. Just a little opinion from me!