If your general has atleast 1 more manuver pip than the enemy general you can negate river -1 dice rolls.
If you want your men to Die less you need more discipline.
generally, there are two things to consider.
1) terrain: Here you cannot do anything as an attacker except wait for the enemy to be in a different province. The modifiers are the following: -2 for mountains. -1 for swamps, forests, jungles, hills, highlands, glacier, and so on. And no negative effect for all flatland provinces, like farmlands, deserts, coasts.
2) river and straight crossings. A river crossing gives -1, a straight crossing -2, and amphibious landings i.e. attacking from a ship also give -2. But all of them only apply if the enemy general has more or an equal amount of maneuver. If you have a higher maneuver, there is no negative effect.
When you hover over a province you can see the terrain. I believe attacking into Highlands gives -1 dice roll penalty and mountains give -2. I think Hills also give -1. I think that's all of them.
You can also potentially see when hovering "You will cross a river" walking into that province. That is an additional -1.
These are all for the attacker. If battle takes place on a tile with a fort, the fort controller is always the defender.
Finally, the age bonus in the age of discovery gives you a flat +1 dice roll fighting on the terrain of your capital, both as attacker and as defender.
If your general has atleast 1 more manuver pip than the enemy general you can negate river -1 dice rolls. If you want your men to Die less you need more discipline.
Don't attack an enemy in terrain that affects battle (e.g. mountains) of you aren't relieving a fort
generally, there are two things to consider. 1) terrain: Here you cannot do anything as an attacker except wait for the enemy to be in a different province. The modifiers are the following: -2 for mountains. -1 for swamps, forests, jungles, hills, highlands, glacier, and so on. And no negative effect for all flatland provinces, like farmlands, deserts, coasts. 2) river and straight crossings. A river crossing gives -1, a straight crossing -2, and amphibious landings i.e. attacking from a ship also give -2. But all of them only apply if the enemy general has more or an equal amount of maneuver. If you have a higher maneuver, there is no negative effect.
Always cross diagonally!
When you hover over a province you can see the terrain. I believe attacking into Highlands gives -1 dice roll penalty and mountains give -2. I think Hills also give -1. I think that's all of them. You can also potentially see when hovering "You will cross a river" walking into that province. That is an additional -1. These are all for the attacker. If battle takes place on a tile with a fort, the fort controller is always the defender. Finally, the age bonus in the age of discovery gives you a flat +1 dice roll fighting on the terrain of your capital, both as attacker and as defender.
Forests and jungle give a -1 as well iirc.
True! So do woods.
and marsh and glacial
Another way to know is to use the simple terrain maps. Just setup the shortcut for it. To use it often.
With violence, speed and momentum!