First of all, regarding the first question: The conditions for destroying the country are: 1. All cities are occupied. 2. The legion is completely destroyed (if there are no more cities or there are too few cities, it will be difficult for the lord to recruit another army after defeating the battle. You only need to occupy all the cities in a country and continue to search for the enemy. After a while, time, the system will show you "XX country was defeated". By the way, the lords of the lost country will join different camps one after another)

Secondly, regarding the second question: solve it. The method is (personal opinion):

1. If you don’t have a fight, you can fight bandits and pirates. If you don’t have enough money, you can do business (except for looting villages, which is the best way to make money). You can go and sit in the village missions to increase the favorability of the village (which is helpful for recruiting troops). In short, there are many meaningful things to do in peacetime.

2. If you are really a war maniac, you don’t have to worry about the country’s policies and curse anyone you don’t like (this will cause dissatisfaction with your monarch)

3. Another trick is that you can switch to a kingdom that is besieged by many countries.

In short, as an ordinary lord, there is no good way to provoke a war between the two countries.