The EO does not accept +Augustine's "just war" theory, never have and never will, even though ti is actually quite reasonable (only as a last resort, never preemptive, and only in defense). The RCCs stick to +Augustine's definition. The Orthodox Church never endorsed any war, although it offers prayers and blessings to solider who are about to face possible death going into combat. That was the prevailing attitude of the early Church, based on Gospels.
The Protestants use the expanded Reformed definition developed in the 17th century onward by various authors, which is more like the OT fundamentalist approach (somewhat based on the "natural law") that the Reformed share with their Israeli friends and Muslim counterparts, namely "I am only doing what God wants me to do." The OT and the Koran are full of such self-rigtheous examples.
Well that explains why the Byzantine Empire fell to the Moslems, and why Hitler found the Balkans such easy pickings, and why those who do believe in a just war had to rescue the people in the land of the EO during WWII.