Heroes of Might and Magic V [Game Discussion]

Hi! I'm playing Heroes 5 and I've encountered a problem. I'm playing through the scenarios, and I can't build a large army. The computer always wins because my army is small. I build up my town well, and I have a lot of money and other resources in the treasury. But I can only recruit soldiers once a week. And even then, only 5, 8, or 10 units. I'm shocked! How can I build a large army? Thanks to everyone. Love you, hugs.