Luca is depicted as a bloodthirsty demon, full of hate and anger, and eventually he was defeated due to his rashness.
Now, the war starts with a false flag operation: a Highland unit killed their own Unicorn Brigade and put the blame on Jowston. The goal of these kind of operations is to justify a war and gain sufficient support for it. In this case, the scheme should furthermore weaken the authority of Agares by suggesting that this tragedy was made possible by the cease-fire treaty that Agares signed.
Was is really Luca who came up with that plan? He certainly doesn’t lack the necessary cruelty, but for its implementation, a certain level of pragmatism and patience is required, basically the opposite of insanity, bloodlust and rashness. Moreover, I wouldn’t say Luca is stupid, but characters like Leon and the Godwins are more convincing regarding this level of political acumen.
"Within the four seas, all men are brothers" Shuihu Zhuan