Yama: War
Normal Attack
This is the common type of invasion. This tactic involves conquering a small portion of the enemies land and resources. 
Planned Attack
This is similar to normal attack except that it involves a more cautious approach on conquering your enemies lands, resulting in more gains and higher chance of winning. However, your military forces will take longer to return from the war.
Raid And Pillage
This is a tactic that involves sending your military forces to loot the opponent's resources. It may not bring you lands, but it does bring in a higher percentage of resources and gives a high chance of success.
Kill Civilians
This is a brutal but effective tactic to slaughter the enemies population. There is no gains from this tactic, however if successful, a huge percentage of the enemy population dies with it.
Sabotage Research
This tactic is designed to penetrate the enemy research buildings and sabotage their research. As a result, the enemy will lose a portion of their research and be less efficient. This tactic has a fairly high success rate.
Destroy Buildings
This is not a very useful tactic, however if successful, it will put a huge portion of the enemy building in ruins.