The Empire found a true friend, the trade is good, Science is exchanged, dependency is guarantied and all the rest.
Our governor wish to create an alliance with them – all is good beside 'Differing war philosophy' which is the only obstacle.
How can our government change policy accordingly, to overcome this last obstacle?
Best Answer
You can't get rid of the differing war philosophy penalty, because that is based on your empire ethics. Instead, you need to get enough bonuses to offset the penalty.
I'd have to do some testing to ensure that this is the case, but here are some things that I believe would help:
Increase their opinion of you. You're already getting a +21 bonus. There should still be some levels higher than that, though.
Some things, like a Non-Aggression Pact, will help not only your opinion, but give a direct buff to the Alliance negotiations. I think Migration Access may help in this way as well. You may not be able to get migration access, depending on your mutual ethics, but one-way is probably better than neither.
You don't appear to be trading with the empire. Trading improves their opinion of you by +5, and may directly impact the alliance negotiations. I often just trade a few minerals a month for a few energy a month.
Common rivals improve relations. Determine who their rival is from the Empire Contacts screen, and declare the same rival.
Common threats improve relations. If they're at war with somebody, go to war with them as well.
If you become significantly more powerful, you can increase the "relative power of empires" modifier.