What is "just war theory"?

Pasi Turunen, theologian (M.Th), author, blogger, and apologist, has been working as a Christian radio broadcaster for over 30 years. He studied theology at Helsinki University, where his master’s thesis dealt with Jewish views on resurrection in the intertestamental Jewish literature. He is the current president of the Patmos Foundation for World Missions, an evangelical missions and relief organization bringing humanitarian aid and the Gospel of Christ to over 20 nations across the world. Here, Pasi answers questions from the talk "How Should a Christian Think About War?", given at the 2023 European Leadership Forum.