The current debate in the United States over the war effort in Afghanistan contains no shortage of opinions on the best strategy for defeating the Taliban, but far too little discussion regarding the actual objectives of the war. The famous Prussian strategist Carl von Clausewitz wrote about war that “the political objective is the goal, war is the means of reaching it, and means can never be considered in isolation of their purpose.” But in the current debate on Afghanistan we risk doing just that — arguing about strategy without a clear understanding of our goals.

So what are the objectives in Afghanistan? What is the purpose for which we are fighting this war? The problem is that they have shifted over time. At the outset, the coalition invasion of Afghanistan was an act of collective self-defense in response to the 9/11 attacks. The objective was to prevent further attack by disrupting and destroying al-Qaida forces operating out of Afghanistan, and overthrowing the Taliban regime that supported them.

These objectives were largely achieved. The coalition has remained in Afghanistan under U.N. authority to establish security in the country, in the face of a simmering insurgency. Now we are debating the best strategy for suppressing an increasingly revitalized insurgency. But before arguing about strategy, the question should be why it is in our national interests, and indeed in the interests of each of the coalition members, to make crushing the insurgency the primary objective.

The two most oft-repeated reasons for the necessity of suppressing the insurgency (aside from vague talk about “winning”), are that doing so would deprive al-Qaida of a base in Afghanistan, and that it would prevent instability and insurgency spreading to Pakistan. Both of these rationales, however, depend on assumptions that are questionable.

First is the assumption that depriving al-Qaida of a base in Afghanistan is essential to our wider efforts against al-Qaida. According to the U.S. national security adviser, Gen. James Jones, al-Qaida is already “very diminished” in Afghanistan. Most reports indicate that al-Qaida’s top leadership in Afghanistan has been decimated, and that the survivors are largely in Pakistan and elsewhere.

This underlines the fact that al-Qaida is a decentralized transnational terrorist movement, not a guerrilla army. Its members can just as easily operate from Yemen, Somalia, Sudan or any number of other bases, often simultaneously. Denying al-Qaida a base for operation may seem a reasonable objective, but large-scale military operations against local forces in every country in which al-Qaida could potentially operate is neither feasible nor would it be effective. It cannot, therefore, be the primary purpose of a counterinsurgency war in Afghanistan.

Part of the problem is that we continue to conflate al-Qaida with the Taliban and other militant forces, both in Afghanistan and in Pakistan. The strategic objectives, methods, and the core ideology of al-Qaida are different from those of the militant forces we are fighting in Afghanistan.

We are fighting a local nationalist insurgency that seeks to gain political power. In general the Taliban and other militant groups, unlike al-Qaida, do not view us as ideological enemies of Islam to be fought on a global stage, but rather they view us as being similar to the British and Soviets of the past, foreign invaders to be driven out. And there is increasing evidence that were the Taliban of today to regain power, it would be wary of again providing the same level of support to al-Qaida.

Turning to the goal of preventing nuclear-armed Pakistan from falling to radical Islamic fundamentalists, the assumption that Pakistan is vulnerable to the spread of radical forces from Afghanistan is similarly questionable. To begin, the Pakistani military is modern, professional, and large (700,000 active duty troops), and is the most disciplined institution in the country. Despite recent high-profile attacks on the military, and the military’s reluctance to use force against its own citizens, the Pakistani Army has shown itself capable of acting effectively against the militants when it has chosen to do so.

We also tend to conflate the Taliban with militant forces within Pakistan, and simplistically view them all as radical Islamists. But they are not the same, and there are tensions and conflicts among them too. There has been no indication that a Pashtun-dominated Taliban could gain control over a country where 1 in 3 people are Punjabi. Ethnic loyalties still dominate Pakistani life and despite isolated attacks in the Punjab, the Taliban has never had a significant presence there. The recent terrorist attacks in Pakistani cities should not be taken as evidence of any desire to overthrow the state, but rather, should be understood as a response to the military operations in the tribal areas. Looking to the historical record, when the Taliban ruled Afghanistan in the 1990s, the situation did not create any instability or cause the spread of radical ideology within Pakistan. And today, according to a recent Gallup Pakistan poll, a full 41 percent of respondents favored military operations against the Taliban.

Beyond denying al-Qaida a base in Afghanistan and preventing the spread of instability to Pakistan, there may be other possible reasons why it is in our interest to maximize the coalition efforts to crush the Taliban insurgency. And it is certainly not in anyone’s interest for NATO forces to withdraw from Afghanistan expeditiously. But if we are going to get the policy right, we must start with the issue of our objectives and the overall purpose for our being in Afghanistan. Only then can we have a meaningful discussion about strategy.

The debate over climate change legislation is beginning to heat up. The American Clean Energy and Security Act was passed by the House and is now before the Senate. The debate on this issue typically takes the form of environmental concerns about global warming pitted against economic fears about the cost of reducing greenhouse gases. It is often framed in left-right terms. But as Americans think about whether to support this legislation, they should ponder the national security implications of climate change.

The recognition that global warming will increase the threats to our national security and place ever greater demands on our military is not new. The Bush administration acknowledged the issue in the 2006 National Security Strategy. A national security think tank comprising retired military officers, including Marine General Anthony Zinni, issued a report on the subject in 2007, identifying the various ways in which man-made climate change will directly affect national security.

Areas of the globe will be increasingly ravaged by drought, on the one hand, and flooding from extreme storms and rising sea levels on the other. These will cause mass migrations of refugees, the breakdown of societies and resulting conflict over reduced arable land, living space and other resources. The conflict in Sudan today is in part caused by the prolonged drought in the region. The massive movement of refugees that followed both the recent flooding in Bangladesh and the typhoon that hit Myanmar are other examples of such climate-related disruption. Climate change is seen as a “threat multiplier” that intensifies instability and sows the seeds of conflict.

Such instability and conflict will affect the United States. Armed conflict and massive political upheavals pose the risk of ever-wider hostilities and thus draw the world powers into the fray if only to contain it. Dislocation and instability will also lead to the failure of states, which become incubators for the development of other threats. Consider Somalia in the 1990s and again today. The failed state of Afghanistan in the 1990s provided a base for the planning and launching of the Sept. 11 attacks. The initial failure of Afghanistan was not caused by global warming, but a study conducted for the National Intelligence Council predicts that climate change raises the risk of many more failed states in the future.

The Pentagon and the State Department increasingly factor these expected ramifications of man-made climate change into their strategic planning and policy development. But the impact on national security should also be part of the broader debate on emissions policy. The greater and more rapid the climate change, the more quickly these threats will emerge – and the greater will be the impact on our national security.

Thus, efforts by the United States to reduce carbon emissions and to lead the rest of the world in tackling global warming are partly an effort to reduce the likely threats to our own national security. As the military strategist Sun Tzu wrote more than 2,500 years ago, the very acme of military skill is never having to fight a battle. General Zinni echoed this wisdom recently, saying “we will pay to reduce greenhouse gas emissions today … or we’ll pay the price later in military terms. And that will involve human lives.”

Some still cling to the tired argument that the link between human activity and climate change has not been “proven.” But in military and strategic matters, we do not wait until a risk has actually exploded into reality or wait for potential threats to be proven before developing our defenses. We defend against our best estimate of the future threat. So even if some holdouts continue to doubt the causes of global warming, prudence still dictates that we act now to respond to the risk.

Of course, the scientific community overwhelmingly endorses the position that humans are causing global warming and that we are near the point of no return. Meaning, unless we take action now, climate change will increasingly and radically multiply the threats to our national security, and the future drain on our military resources will dwarf the economic cost of taking action today. And we will pay in blood as well as treasure. That is something we would do well to remember when we consider the climate change bill before the Senate.