Why Congress must vote on Obama's war with IS

Some wars are necessary. Yet war itself is human folly. Reconciling these two seeming truths will long remain a challenge, President Obama stated in a 2009 speech accepting the Nobel Peace Prize.

Now in 2014, as he revs up the American military to “destroy” the Islamic State (IS) militant group in a war that may outlast his time in office, Mr. Obama is throwing this challenge back on Americans. Will they help him reconcile these two aspects of war?

He has welcomed Congress providing legal backing for him to bomb IS in Syria and Iraq and to deploy military advisers there. Yet he also claims he already has such authority under the post-9/11, Bush-era authorizations for war on Al Qaeda and in Iraq. His request may be really aimed at gaining political and moral support for war actions already begun in Iraq – perhaps just in case the war goes badly and a blame game erupts.

But precisely for these reasons, many members of Congress are hiding in the weeds. Lawmakers have decided to wait until after the midterm congressional election in November to vote on any approval for the war, or for a measure known as an Authorization for Use of Military Force (AUMF). In a warm-up for that vote, they are voting this week on authorizing money for the United States to arm “moderate” rebels in Syria.

The American people deserve a full-throated debate in Congress on the causes, purposes, and conduct of the war against IS being fought in their name. Is this a war of self-defense or simply the defense of others? Will it bring a just and durable peace? What non-war means might achieve the same goals? And what restraints can be placed on this war, such as its duration or the tactics used to avoid civilian deaths?

These are not easy questions, which explains why lawmakers should be granted the liberty to vote their conscience on a war measure. Such a debate should also be done without emotion, such as revenge for the IS beheading of two Americans, or for sectarian motives, such as attacking Islam.

And given past atrocities committed by American troops in recent wars, the US must make doubly sure that this war is legally secured on the highest moral ground. The means of war are as important as its ends.

The wars against Al Qaeda, and now IS, are somewhat unique in the history of American warfare because they call for total destruction of the enemy. While this is not quite genocide, it does raise difficult questions about sticking to a principle of warfare known as proportionality, or moderation in choosing targets and allowing for an enemy to plead for peace.

IS commands an estimated 10,000 fighters and controls a territory roughly the size of New England. Obama plans to rely on ground fighters in the region to wipe out this budding caliphate, with US air support. Yet his commanders also say they would recommend using US combat forces if Americans are attacked by IS.

The chance for mission creep, or a “slippery slope” toward wider war, also requires Congress to act with a solid moral footing – and wide public consensus – before passage of an AUMF. War can quickly turn to folly if its motives and tactics are not in line with highest principles.

Congress is off to a bad start by not holding this debate before the election. Being held to account for a war is one way to reduce its potential folly. But even in a lame-duck session, lawmakers can still rise to the occasion and make sure Americans know the causes, purposes, and conduct for a war already being waged.