Over six years ago, U.S. President Barack Obama came into office with a firm conviction that the United States needed to revitalize its alliances and renew its core security relationships around the world. That is why one of the most important tenets of his foreign policy has been to build strong partners. The Obama administration’s 2015 National Security Strategy makes clear that while the United States needs to continue to lead, it must do so with “capable partners” and that “no global problem can be solved without the United States and few can be solved by United States alone.”

The National Security Strategy goes on to state that when it comes to addressing the world’s most pressing security challenges, “a strong Europe is an indispensable partner.” The United States views a Europe more capable of tackling security challenges — and therefore sharing the burden — as essential to ensuring maintenance of a strong transatlantic alliance. That is why a meaningful division of labor between the United States and Europe is vital to having a strong partnership.

Of course, countries will have competing priorities, influenced by differences in geography, economics, or history. One cannot expect that all countries will prioritize everything equally; what matters are the big issues. The United States and Europe must have a common outlook and be willing to share sacrifices. From a U.S. perspective, a division of labor means that the United States is not expected to do everything alone, and that Europe is prepared and willing to put substantial resources into meeting security challenges.

This is what Obama has set out to do. He has tried to ensure that where the United States is contributing to common efforts, it does not necessarily own the effort outright. Obama has focused on the U.S. contribution being defined through what he calls “unique capabilities.” The United States must lead, but do so in a way that enables other partners to contribute as well.

For example, in the 2011 Libya campaign, the president was determined that the United States resist the temptation to dominate the intervention, and instead, sought to “cabin” the U.S. role to providing unique capabilities like intelligence, surveillance, and reconnaissance (ISR) assets; airlift and refueling; and precision strike. Obama was also determined to make it a NATO effort, drawing the capabilities of others into the campaign. In the end, 18 countries were involved and U.S. forces flew just over 10 percent of the strike missions. The campaign’s success would not have been possible without NATO’s command and control capabilities. As then-U.S. National Security Adviser Tom Donilon observed at the time, “This approach succeeded in meeting our objectives and led to a division of labor that enabled others to contribute based on their distinctive capabilities and interests.”

There is a similar dynamic in addressing other common challenges. Take Afghanistan, where the United States and Europe have worked together in what has been the longest NATO operation in history. And in West Africa, the United States is using its unique capabilities to support the French in its military operations through intelligence, airlift, and refueling support.

There has also been a division of labor in the transatlantic community’s response to the Ukraine crisis. Both the United States and Europe have stepped up on sanctions, despite the fact that many predicted the Europeans would never be able to muster the will to do so. European leaders have been at the forefront of the diplomatic effort to try to solve the crisis, with the United States in support. Yet the United States is putting more emphasis and resources toward working with the Ukrainian military to ensure that it becomes more capable, less corrupt, and that it can play a positive and stabilizing role in its country (of course, this is an area where the United States would like to see more European involvement). So far, the United States has committed to providing the Ukrainian military with over $200 million in assistance. Beyond Ukraine itself, the United States and Europe have been sharing the burden in reassuring NATO partners in the East through such initiatives as the Readiness Action Plan and by bolstering NATO’s rapid response capacity.

In the Middle East, the United States and Europe are sharing the burden in the campaign against the self-proclaimed Islamic State group (ISIS). While the United States is doing the most by far, it is not alone. France, the United Kingdom, the Netherlands, Belgium, and Denmark are taking part in direct airstrikes against ISIS in Iraq. Germany sent 40 paratroopers to conduct weapons training in Iraq last fall, and Kurdish fighters are also being trained in southern Germany. The U.K., Spain, Portugal, and Italy have also sent or committed troops for the training effort. France, Germany, the U.K., the Czech Republic, Estonia, Hungary, and Albania have provided direct military assistance, while many others have provided monetary support. That is all good, but the campaign against ISIS will not end anytime soon. The real test will be in sustaining European capabilities, resources, and public support throughout the campaign.

These examples illustrate why the debate about defense investment and capabilities matters so much. In a way, a division of labor is inherent for Europeans, since U.S. capabilities are so dominant. From Washington’s perspective, the perception is that transatlantic labor has not been divided enough. To be simplistic, the United States does not want the desire for a division of labor to become an excuse for Europeans to shoulder the burden on the “easy” security problems and for the United States to take on the “tough” ones. U.S. national security leaders are no longer worried about Europe duplicating capabilities or diluting NATO; they are concerned about Europe evolving into strategic irrelevance — therefore making it impossible to divide the labor.

This points to the core challenge: Inherent in the concept of dividing the labor is the idea that the United States and Europe have the same perspective on security threats, and that there is a common cause that transatlantic partners must bring their different capabilities to help address. When it comes to issues that threaten the NATO Alliance, and the broader transatlantic homeland, cooperation between the United States and Europe is paramount.

Over the years, Americans and Europeans have shown that they do have that shared perspective, despite the popular argument that they come from different planets. The United States and Europe have worked and sacrificed together in places like Afghanistan, where there are still thousands of U.S. and European troops trying to help bring peace to that country. Similarly, against ISIS, the United States and Europe have a shared perspective of the urgency and magnitude of the threat. And finally, on Russia, the United States and Europe increasingly see eye-to-eye on the great danger that President Vladimir Putin’s Russia poses.

To address such issues, the United States wants and needs strong and capable partners. “A core principle of all of our alliances is shared responsibility,” then Secretary of State Hillary Clinton said a few years ago. “Each nation must step up to do its part. And American leadership does not mean we do everything ourselves. We contribute our share — often the largest share — but we also have high expectations of the governments and peoples we work with.” That is why Washington wants a Europe that is willing to invest with the United States in common security efforts. That is why it wants more capable European militaries. And that is why, when it concerns to common security efforts, the United States believes it must share the burden, and yes, divide the labor. In a world experiencing such dramatic and historic changes, which present so many security challenges to the transatlantic community, we cannot afford to do anything less.