Diplomacy may be the art of statesmanship, but intervention is rarely artful. Whereas diplomacy happens comfortably behind tables, intervention often unfolds dangerously on the ground. Surely one of the most intriguing methods of state-to-state interaction, intervention is also one of the most wide-ranging in form. Many prominent scholars, for example, point to subtle economic and cultural intervention as natural corollaries to liberal trading regimes. Even military interventions may be covert. But intervention is still widely interpreted in its classical, realist sense to mean overt military operations by one state within the borders of another. It is this variety that our symposium seeks to explore.

Motives for intervention have varied over the centuries. Geopolitics, for one, has provided a historically powerful impetus for intervention. In the wars preceding the Treaty of Westphalia in 1648, states intervened to diminish the absolute sovereignty and relative material factors of their rivals. Other interventions, as in East Timor in 1999, have focused on creating functional systems of governance. Along with geopolitical justifications are those based on rights. The Rwandan genocide of 1994 sparked debate over whether governments forego their right to sovereignty when they commit crimes against humanity within their own borders. Somewhere between these consequentialist and deontological justifications for intervention lies the institutionalist claim that intervention may occur to uphold international common or positive laws.

All of these justifications betray a certain irony: states wage war to make peace, foster temporary instability for long-term stability, and transgress certain laws to uphold others. On its face, then, the use of force is hardly appealing. So when are these seemingly paradoxical interventions justified? While positivists point to existing international law, liberals appeal to broad consensus on norms or to certain inalienable rights, and realists may argue for the necessity of self-defense. Yet each of these answers raises only more questions. Can international law be natural, wherein states lack absolute freedom to establish their contractual relations? Are there norms outside international law that should govern state-to-state behavior? Or is international law legitimate only when it is positive—explicitly constructed and ratified by states? And when does self-defense creep toward offense?

The origins of classical intervention are difficult to pinpoint. In earlier times, intervention found legitimation from religion. Intervention later became a tool in the geopolitical race for the conquest of new and the maintenance of old territories. Later still, a coalition of liberal democracies changed intervention into a means for upholding a set of norms. Now, an era of additional interventions, different justifications, and new doctrines leaves us with a fresh set of questions. It is these questions of when, how, why, and where interventions occur that our symposium addresses. Michael Walzer answers challenges to the use of just war theory, while Richard Falk examines the resurgence of just war arguments and the corresponding diminishing emphasis on legal support in cases of intervention. Jon Western traces the historical trajectory of US interventions and observes the significance of public support in launching such operations. Bartram Brown considers whether the international legal system can justify recent interventions and whether its laws can be adapted to formulate clear standards for the future. Kenneth Roth specifically examines the case of Iraq, concluding that US actions there breached present standards of humanitarian intervention. Alan Kuperman questions the benefits of intervening and suggests reform of the current humanitarian military intervention system. Finally, John Prendergast and David Mozersky use instances of external involvement in Sudan’s civil war to frame a discussion of regional interventions.

Intervention continues to come under increasing scrutiny, especially in light of the most recent events in Afghanistan and Iraq. As the fallout from these and other interventions becomes apparent, the international community must be able to modify the existing doctrine that underlies intervention. Each new catalyst for conflict and impetus for intervention demands a re-assessment of the necessity for involvement. Only through such constant vigilance can future interventions—if any—be justified by those who feel they must step in.