One of the conditions for a war to be just (morally justifiable) is stated in the Catechism of the Catholic Church as: “there must be serious prospects of success”. The reason for this condition is that a war to defend a nation would be expected to result in much harm and many deaths, and so, if success is unlikely, less harm would be done by surrender. That’s the theory.
In the case of an offensive war, i.e. the nation engaging in just war is the aggressor, it may be true. As the saying goes: “Don’t start none, won’t be none.” If there is little hope of success, the nation should refrain from going to war. For the good hoped for by the war is unlikely, and much harm and death is almost certain to accompany any war. When an act can be reasonably anticipated to do more harm than good, it is immoral to choose that act.
However, in a defensive war, this criterion of a likely success is not entirely necessary for the war to be just. If you don’t go to war, the attacking nation still attacks, causing much harm.
Suppose nation A attacks nation D. The leaders of nation D realize that they cannot win the war. But they also reasonably believe that, by defending themselves, they will reduce the military resources of nation A. As a result, nation D may be able to mount a second war, in the future, to free their nation. Or they may be able to prevent nation A from going on to attack and conquer other nations.
But if nation D surrenders, then nation A will be able to add the military resources of D to those of A, and subsequently conquer nations that A could not have hoped to conquer with only its own resources, especially if those resources were decreased by a war with D. Therefore, nation D can defend itself, morally, without likelihood of success, because the totality of the foreseeable consequences of that war, for all persons concerned, favors going to war.
An example from history:
“The phrase [molon labe] was reportedly the defiant response of King Leonidas I of Sparta to Xerxes I of Persia when Xerxes demanded that the Greeks lay down their arms and surrender. This was at the onset of the Battle of Thermopylae (480 BC). Instead, the Greeks held Thermopylae for three days. Although the Greek contingent was defeated, they inflicted serious damage on the Persian army. Most importantly, this delayed the Persians’ progress to Athens, providing sufficient time for the city’s evacuation to the island of Salamis. Though a tactical defeat, Thermopylae served as a strategic and moral victory, inspiring the Greek forces to crush the Persians at the Battle of Salamis later the same year and the Battle of Plataea one year later.” [Wikipedia]
Other hypothetical examples
Suppose that nation A attacks nation D with the clear intention of destroying the entire people of nation D. Such a war by nation A is a genocidal war, and therefore intrinsically evil and exceedingly wicked. Is not nation D justified in defending itself, with all its resources, even without serious prospects of success? And if they pray to God for assistance, in a war where they have no reasonable chance of successfully defending themselves, will He not help them, perhaps in an unexpected way?
An example from history :
In 1281 AD, “the Mongol army, led by Kublai Khan, grandson of Genghis Khan”, attempted an invasion of Japan “with an enormous fleet of 4,400 ships and an estimated 70,000 to 140,000 soldiers.” [Ancient Origins]
The Japanese people had nowhere near enough troops to repel this overwhelming force. Subsequent to a previous invasion attempt, they had built two-meter-high walls along the shores, to make it difficult for ships to land troops. But it was only a matter of time before the ships found a place to assault the beaches. The Japanese had no serious prospects of success. So the emperor called for the people to pray.
“Beginning August 15, the now-famous kamikaze, a massive typhoon, assaulted the shores of Kyūshū for two days straight, and destroyed much of the Mongol fleet.” [Wikipedia]
The storm obliterated the attacking army: “over 4,000 ships were destroyed and 80 percent of the soldiers either drowned or were killed by samurai on the beaches in what became one of the largest and most disastrous attempts at a naval invasion in history.” [Ancient Origins]
The idea that a nation cannot morally defend itself unless there are “serious prospects of success” is not a necessarily condition for every war to be just. Some wars can be just without meeting that condition. The prospect of success certainly weighs in the third font of the circumstances in considering the morality of going to war. But it is also, just as certainly, not an absolutely essential condition that must be met in all cases. Some circumstances can make going to war moral, despite little hope of success.
Speaking more generally, I believe that the traditional just war theory needs to revised in the light of recent teachings of the Magisterium on morality, especially the teaching of Veritatis Splendor on intrinsically evil acts and the three fonts of morality.
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