How a war ends often depends on how it began. Take the one that boiled over in Somalia last week. Islamist forces attacked a legal government guarded by an invading Ethiopian army. Which side had just cause? The answer isn't so easy.
Both the UN and the African Union, two international bodies that often intervene in sovereign nations, largely stood by, argued, or scratched their collective heads as the fighting in Somalia raged on. Secretary-General Kofi Annan declared a UN-backed intervention was not needed.
The Islamists, known as the Union of Islamic Courts (UIC) and made up of various religious clans in Somalia, declared "holy war" Dec. 20 and invited foreign jihadists to join in. Neighboring Ethiopia, a largely Christian nation, claimed the UIC was meddling with Ethiopia's Muslim minority. And the US (supporting Ethiopia) claimed the Islamists were creating a terrorist state, using child soldiers, and committing Taliban-like abuses.
Thursday, with the Islamists having lost control of Somalia's capital, Mogadishu, world diplomats were still trying to figure out how to apply lessons learned from conflicts of the past 15 years, such as Rwanda, Bosnia, East Timor, Kosovo, and the US military's disastrous 1992 food mission in Somalia.
Each of those conflicts has added various types of rationale to an ongoing debate over how to justify outside military intervention in a troubled nation or between nations.
The 1994 genocide in Rwanda, in particular, led Mr. Annan to back "humanitarian intervention" if a state fails to protect its people from genocide, war crimes, ethnic cleansing, or crimes against humanity.
Annan, who leaves office next week, won support for this so-called responsibility to protect at a 2005 world summit. It is perhaps the most significant legacy of his 10 years as UN chief.
But the move hardly settles the debate, especially as the international community has done little to stop the killings in Darfur. The world also has yet to come to terms with the Bush doctrine of preemptive intervention against terrorists or terrorist- supporting nations. The UN endorsed the 2001 invasion of Afghanistan to preempt another Al Qaeda-led attack on the US. But it didn't back the 2003 US-led invasion of Iraq.
Ethiopia preemptively moved to protect a Somali government recognized by most nations but besieged by the Islamist forces. It had the tacit approval of many African and Western nations. But not the UN.
The Islamists, on the other hand, had temporarily brought order to the capital and other parts of Somalia after 15 years of no effective central government and chaos under competing warlords. They also won support from many nations.
This conflict exposes the difficulty in defining general principles and thresholds to justify outside intervention while also contending with the self-interests of UN member states. Even if a need for intervention is clear, as with Darfur, finding a military force to do it isn't easy. And unintended consequences, as with Iraq's civil war, can result.
Successful interventions by the UN and others have set the groundwork for deciding future interventions. But the Somalia war shows more work still needs to be done.