Just-war theory is complicated, but we can highlight the principles as well as some issues pertaining to the current situation in Syria. For a more detailed explanation of just-war theory, consult previous Straight Answers. All Catholics need to understand church teaching on war and how it applies to this troubling situation.
In the beatitudes, Jesus taught, “Blessed are the peacemakers.” Real peace, however, must be built upon love, truth, justice and mercy. To have peace means a person or even a country must at times confront the forces of evil that seek to destroy peace. Therefore, making peace entails legitimate acts of self-defense, which may result in taking the life of an unjust aggressor. Therefore, Vatican Council II affirmed that “governments cannot be denied the right of lawful self-defense, once all peace efforts have failed” (“Gaudium et Spes,” No. 79).
Just-war theory provides the moral principles for the declaration and waging of war. St. Augustine (d. 430) was the originator of the just-war theory, which St. Thomas Aquinas (d. 1274) later explicated in his Summa Theologiae. Of course, since the Middle Ages, warfare has changed dramatically. Nevertheless, given St. Augustine’s and St. Thomas’ foundation, just-war theory provides the following principles: In preparing to wage a just war (ius ad bellum), a country must meet the following criteria:
1) Just cause. The war must confront an unquestioned danger, avenge a wrong, or restore what was unjustly seized. As the catechism teaches, “the damage inflicted by the aggressor on the nation or community of nations must be lasting, grave and certain” (No. 2309). In the case of Syria, the United States has not been attacked nor is its national interests at risk. A country does not have the right to interfere at will in the internal matters of another country, especially to remove a legitimate leader or government, albeit a dictatorship, and especially when the opposing forces are a conglomeration of rebel groups.
2) Proper authority. The legitimate authority must declare the war and must be acting on behalf of the people. For the United States, only Congress has the power to declare war, and the War Powers Act limits the president’s use of military intervention on his own initiative. Moreover, international law, in accord with the charter of the United Nations, demands that force only be used in the case of self-defense or by a decision of the U.N. Security Council.
3) Right intention. The reasons for declaring the war must actually be based on just objectives and not a masking of ulterior motives. St. Augustine also noted that just wars are “those wars that are waged not for motives of aggrandizement or cruelty, but with the object of securing peace or punishing evil-doers, and of uplifting the good.” One must ask, “What is the intention of the United States to act on its own, using missile strikes?” To establish democracy? President Putin commented, “There are few champions of democracy in Syria. But there are more than enough al-Qaida fighters and extremists of all stripes battling the government.” Melkite Greek Catholic Bishop Nicolas Antiba of Bosra and Hauran in Syria said, “You (Americans) have your own idea of democracy and it is beautiful but it is not necessarily our idea of democracy; let us work out our idea of democracy.” Moreover, can the intention of the United States be pure in acting to help the Syrian people knowing that Islamist terrorist groups from other countries have infiltrated with the intent of establishing an Islamic state? Or, is not our intention corrupted when the rebels the United States are supplying are linked with organizations that have attacked our own country?
4) Last resort. All reasonable peaceful alternatives must have been exhausted or have been deemed impractical or ineffective. The contentious parties must strive to resolve their differences peacefully before engaging in war, e.g., through negotiation, mediation, or acts like embargoes. Pope Francis, Putin and many others have called for diplomacy and negotiation, before resorting to military action. Putin noted, “No one wants the United Nations to suffer the fate of the League of Nations, which collapsed because it lacked real leverage. This is possible if influential countries bypass the United Nations and take military action without Security Council authorization.”
5) Proportionality. The good that is achieved by waging war must not be outweighed by the harm. What good is it to wage war if it leaves the country in total devastation with no one really being the “winner?” Modern means of warfare give great weight to this criterion. Given the experience of Iraq, Egypt, Libya and Tunisia, will removing a dictator and leaving a country at the hands of terrorist organizations, like al-Qaida, al-Nusra Front, and the Islamic State of Iraq and Levant bring peace or a greater stability to the Middle East?
6) Probability of success. The achievement of the war’s purpose must have a reasonable chance of success. A country must not declare war knowing it will probably lose. Given the experience in Afghanistan, will outside military action lead to success in the long-run or just reduce Syria to fighting among extremists and destabilize the already fragile Middle East?
Read Father’s answer to the question, “What are the criteria for waging a just war?“