This is a really bad idea. Spies can get pretty expensive, in both upkeep and use, so your suggestion would basically ensure small-midsize nations have no idea what any nations around them have for a military since maintaining a decent number of spies and using them would be prohibitively expensive. In addition, you only get one spy use per day, and I can't think of anyone who would want to waste that use, and spend a good chunk of cash ($10,000 per spy at the most basic level) just to find out what another nations military is. If you wanted to keep an eye on someone for a couple days, you would never have any spare cash, just be spending it all on spies. To make it worse, your idea would only allow for partial army counts or a high chance of failure, ensuring you will never get a full picture. I mean, say you are in a war, and want to see your opponents army. You will send a spy raid over, and either see a random percentage of their troops, or fail completely. Either way, you will have no real idea of their strength, and will have wasted the money you could've used to support your military, leaving you with less than you started, and easily crushed. Of course, your opponent will have the exact same problem, meaning war will suck. To restate, this is a really bad idea, and shouldn't happen.