There are many bonuses that you can apply in battle. Equipment, Research, Seats of Power, Boost Items, can all have bonuses that improve the odds of defeating your opponent.
If you tap on your Lord's Portrait and select the "Stats" Tab, you can see all of your active bonuses. Scrolling further down the Stats tab, you can see how your Equipment and Research is increasing your bonuses as well.
If you are curious about what specific bonuses applied to a recent battle, be sure to tap the 'View Details' button on your Battle Report, and then tap the 'i' next to any player involved in the battle. Under the 'Stats' heading, it will list all stats that applied to the battle.