When the leaders of the European Union’s 28 member states gather in Brussels for one of their regular summits on December 19 and 20, it will be the first time in five years that defense policy is on their agenda. In that interim, Europe’s defense deficit has dramatically worsened -- that is to say, its military capabilities have deteriorated as its military needs have increased. If the continent’s leaders fail to do something to reverse this trend, they will almost surely come to regret it in the years ahead. For too long, Europeans have been in denial about the way forward. They must finally agree to collaborate on defense policy.

In the words of Catherine Ashton, the EU’s high representative for foreign and security policy, Europe foreign policy faces “increased volatility, complexity and uncertainty” in the years ahead. The Arab Spring and the war in Syria continue to spill over into Europe in the form of refugees and an increased threat of terrorism; meanwhile, Russia continues to insist on asserting control over a sphere of influence in Eastern Europe, particularly in Ukraine. At the same time, Europe’s prosperity has never been more dependent on the maintenance of secure trade routes abroad. Keeping sea-lanes open is a particular priority, since 90 percent of European trade is transported by sea. There is no shortage of foreign policy challenges that crucially affect European interests, if not European survival.

Until now, Europe was mostly content to rely on the United States to take the lead in addressing such matters. According to an analysis by the office of the NATO secretary-general, the share of the NATO defense burden falling on the United States has increased from 63 percent in 2001 to 72 percent today. The average defense spending of the United States’ NATO allies was 2.0 percent in 2000 and had slumped to 1.5 percent by 2007. This state of affairs has only worsened with the onset of the economic crisis.In contrast, the United States spends 4.6 percent of its GDP on defense.

But it is no longer viable for Europe to outsource its defense requirements. U.S. President Barack Obama has made clear his distaste for committing U.S. forces to foreign military adventures, and a recent Pew poll confirms that the U.S. public feels the same. Furthermore, U.S. strategic priorities have shifted; Obama administration officials have explicitly said that, as a consequence of Washington’s rebalancing to Asia, Europeans will have to play a bigger role in securing their own neighborhood.

But there are few signs that Europeans are up to that task. Especially since the onset of the global financial crisis and the EU’s currency crisis, European states have neglected their own military capabilities. Strong militaries cost money to build and maintain -- money that many cash-strapped European governments have preferred to spend elsewhere. Europe’s austerity programs have hit its defense budgets especially hard. Germany and the United Kingdom have made reductions of about eight percent over the last several years. But some smaller member states have initiated more dramatic reductions of 20 percent or more. Lithuania cut its defense budget by an astonishing 36 percent in 2010. Little wonder that NATO Secretary-General Anders Fogh Rasmussen warned that “if European defense spending cuts continue, Europe’s ability to be a stabilizing force even in its neighborhood will rapidly disappear.”

Beyond the problems caused by falling defense spending, European militaries are suffering from their failure to coordinate their policies with one another. At a time when joint military deployments have become the norm, each national military in Europe is still separately trained, equipped, and supplied. When countries make cuts to their military programs, they do so without consulting their partners. The result is that, when European forces try to cooperate in the field, they are hampered by incompatible equipment and deep-seated doctrinal differences.

Europe’s military fragmentation also causes vast economic inefficiencies. The majority of national defense budgets is spent on national armed forces equipped with nationally produced weaponry. Indeed, European governments have often treated defense policy as a means of propping up national champions -- in a manner, incidentally, that the EU long ago outlawed in civilian sectors. In 2009, member states had a total of 89 active weapons programs. (Contrast that to the United States’ 27.) Needless to say, many of Europe’s programs overlap. The European Commission estimated the cost of barriers between national defense markets -- including the costs imposed by incompatible weaponry and by closed systems of national procurement -- as over 3 billion euros per year.

The results of Europe’s defense deficit have been all too evident during recent military interventions. Although France and Great Britain were widely credited with taking the lead in the intervention in Libya, the United States provided more than twice the personnel than either. Europeans were forced to rely on the United States to provide Tomahawk missiles, drones, and electronic warfare aircraft, which proved decisive in the conflict. European countries even had to reduce their presence. Air sorties were cancelled due to lack of munitions. The French were forced to pull back their only aircraft carrier for maintenance while the Italians withdrew theirs because they claimed they couldn’t afford to keep it deployed for any longer. The United States had to plug all the gaps.

Yet despite the obvious inefficiencies caused by their failure to collaborate on military policy and procurement, European states have repeatedly failed to take any steps to correct it. There has been plenty of rhetorical commitment to the cause: since creating the EU’s Common Security and Defense Policy in 1999, member states have issued a number of statements of intent, capability targets, and “headline goals.” But none of that has resulted in action. Europe continues to lack all of the key military equipment -- air-to-air refueling capacity, intelligence surveillance and reconnaissance, and satellite communications -- that has been serially identified as lacking in EU reports. Nor have European member states provided the EU with the authority to liberalize the European arms market, let alone plan or run military missions.

Some of the pressures against military collaboration are entirely understandable. All governments are inherently reluctant to share control over their defense policies. Relying on others for security is a risky business, particularly when, as in the European Union, member states have widely different conceptions of the nature of the threats confronting them. And the short-term pressures to favor national industries will always be immense. For all the military problems generated by relying on small-scale national defense industries, they generate politically valuable jobs and skills.

But European governments can no longer afford to act as if Europe’s defense deficit did not exist. The United States is not willing to continue to make up the difference, and the threats to European security are mounting. As a first step, at the upcoming summit in Brussels, Europe’s most senior political figures must enhance their collective strategic awareness. They must acknowledge the threats they face and the profound limits on their ability to address them individually. Simply by delineating their security interests, European states would reveal a broad convergence between them. Similarly, national capitals must agree to review the military capabilities at their disposal, so that they can curtail the acquisition of capabilities that Europeans collectively do not need, or prevent cutting capacities that are already in short supply in Europe as a whole. Nor can the summit be a one-off event. There must be follow-through, perhaps taking the form, as suggested by Ashton, of a strategic level defense road map, along with a “European defense reporting initiative” to synchronize budget planning cycles and set benchmarks for policy collaboration.

History suggests that the December summit is unlikely to achieve anything dramatic in terms of Europe-wide military collaboration. But it would represent a damning failure were the European Council’s first discussion of defense since 2008 to end without agreement on some practical moves forward. The engagement of national political leaders in such a collective process would mark a necessary first step in the development of greater strategic awareness. Europeans could discuss both the threats they face collectively and their limited individual means for addressing them. It is only on the basis of such awareness that they might, haltingly, begin to address the defense deficit that afflicts them all.