Over the millennia, wars have defined nations and society, carving the very history of humanity. Even today, in particular conditions, we found ourselves susceptible to the innate nature of war. It was not uncommon that much of these involved the brutal and unrelenting slaughter of man, much of which went ultimately unpunished. This would imply that during war, there is a void of our previously held value for human life, finding our justification for war a greater cause. If so then, what is a just war? How can we justify hypocritically killing human life in war if we denounce it so much?
In 13th century, western philosopher Saint Thomas Aquinas wrote a publication documenting and outlining Jus in Bellum theory (the right to war), notating what was traditionally considered implicit “rules” and common “moral values” when it came to one’s conduct in war. These involved, notions of minimising loss of innocent civilian life, settling the war motivating rationale as promptly as possible and restricting infrastructural damages.
First, war must occur for a good and just purpose rather than for self-gain (for example, "in the nation's interest" is not just) or as an exercise of power.
Second, just war must be waged by a properly instituted authority such as the state.
Third, peace must be a central motive even in the midst of violence.
This was further elaborated by