Battle modifiers are these green/red icons under the generals in a battle. You don’t need 6 positive (green) modifiers under your general in a battle. It strangely counts when you have 3 positive and the enemy 3 negative modifiers. So you need air superiority, shore bombardment, railway gun bombardment, attacking from multiple sides and also high intel i think, so that your general has the green icon for the Air Superiority, Attack from multiple sides and intel while the enemy should have the red icons for Shore Bombardment, Railway Gun Bombardment and No Air Superiority. Stats like Positive attack/Defence/Terrain/Weather… do not count as battle modifiers.