Israel last week submitted its response to the UN's Goldstone Report. That report investigated the conduct of Israel and Hamas during the Gaza war in January 2009, accusing both sides of war crimes. It recommended resorting to the International Criminal Court if the sides failed to investigate the charges themselves. One of Goldstone's sharpest accusations, denied by Israel, was that Israel used incendiary phosphorous artillery near civilians, against the laws of war.

The Goldstone report and Israel's response point to some of the most important questions facing Western democracies today: when can our nations legitimately resort to military action, and what is permissible in the course of military action? What are we allowed to do to defend ourselves?

Different nations have had their own codes of warfare to describe acceptable purposes and means in warfare. Growing out of work by Augustine and Thomas Aquinas on just war theory, efforts in the West beginning with the 19th and 20th century Hague and Geneva conventions aimed to limit the impact of modern warfare on civilian non-combatants and on combatants themselves, as well as to define what circumstances permitted a nation to go to war.

The call for such rules heightened with the carnage of the 20th century world wars. A single night's American incendiary bombing of Tokyo in March of 1945 killed some 100,000 people. Fire bombings of London, Coventry, Dresden, and other European cities during World War II - undertaken by two sides with very different motives but similar means - killed tens of thousands.

These acts of war, like Israel's actions in 2009, raised hotly contested questions of "proportionality" as defined in just war theory. Proportionality demands that a military act be proportionate in its effects on civilians to the expected military gain. Just war theory also tries to distinguish combatants from non-combatants, with special protections for the latter.

The United States, Germany, and other NATO countries have faced questions on the proportionate nature of their actions in recent years. The German military's call for an air attack in Afghanistan last fall, which killed 69 enemy combatants and some 30 civilians, provoked a political and moral crisis in Germany. The United States has, to say the least, been criticized both for its reasons to go to war in Iraq and for its conduct of the wars in Afghanistan and Iraq. Such criticism is not new. The Vietnam War was as contentious as Iraq for its purposes and methods (including incendiary napalm). U.S. Presidents Ronald Reagan and Bill Clinton faced criticism for their reprisals against Libyan and al Qaeda terrorists, respectively. Conversely, Western nations were charged with disproportionately weak responses in the Balkans in the mid-1990s.

Such vigorous debates are proper in democracies that seek to guide their actions by considerations of law and justice, though formal inquiries are often begun only reluctantly and political considerations always intervene. Such is the nature of democracy. In its response to Goldstone, Israel indicated that it had disciplined two field commanders and that 150 allegations of misconduct during the war have been investigated, with 36 referred for further criminal investigation. This is the way Western democracies handle complex and difficult questions of accountability, even though these debates put Western militaries under constraints and pressures their enemies do not share.

And the questions are indeed complex and difficult. Other related questions in just war conduct have become more ambiguous yet more urgent as terrorists and insurgents emerge as the main enemy. The distinction between combatants and non-combatants is less clear. Should terrorist abettors be treated as combatants? How does one handle cases of an enemy employing "human shields" or deliberately placing military capabilities in civilian facilities, a particular problem in Afghanistan, Iraq, and Gaza? What about civilian workers in a defense ministry or an arms plant?

The Goldstone report charged Israel with taking disproportionate actions and disregarding the safety of civilians. The contrast between the fire bombings of World War II, with massive death tolls for civilian populations, to the 1400 deaths in Gaza (some significant proportion of whom were combatants) shows how far the standards for proportionality have come in the minds of some observers. Obviously, such measures do not demonstrate the proportionate quality of any act. But Israel clearly did not use anything like its full military capacity in Gaza (an indication of restraint, though again not a guarantee of proportionate action). And Israel appears to have gone to great lengths to limit civilian deaths. Yet these constraints were not enough to preclude the strong criticism of the Goldstone report.

The West - including especially Europe, the United States, Canada, and Israel - needs a new consensus on these questions. Specialized groups of lawyers and military experts have engaged in efforts to resolve these issues. Those efforts continue, and they are an important part of answering the questions. But, the German Marshall Fund's recent Transatlantic Trends poll showing that 70% of Europeans do not agree that the use of force is sometimes necessary to obtain a just outcome, while at the same time 70% of Americans agree with the statement, a broader and deeper transatlantic discussion on the use of force is essential. Such a discussion will not eliminate accidents or failures in war. But it might allow the West to respond to its enemies with greater confidence in its own purposes and methods.