NATO was founded 70 years ago to prevent war between the liberal-democratic West and the Soviet East. The fact that the Cold War never turned hot is a testament to its success. Moreover, whenever NATO has deployed troops, it has been authorized to do so by the United Nations Security Council or the Organization for Security and Cooperation in Europe (OSCE). The oft-criticized exception was its intervention in the Kosovo War; but in that instance, it put an end to an ethnic cleansing that was already underway.

NATO's primary purpose is collective defense. Article Five of the North Atlantic Treaty – which holds that an attack on one member is an attack on all – is as necessary today as ever before. It is why West Berlin remained free throughout the Cold War, and why Poles, Estonians, Lithuanians and Latvians today can rest assured that their freedoms are secure. Those who blame NATO's eastward expansion for Russia's incursions in Ukraine implicitly deny that former members of the Soviet bloc have the same right to freedom and security that other NATO members enjoy.

Historically, NATO's strength rested on its ability to reach consensus despite partners' differing starting positions. The organization has proven its capability to adapt to changing global contexts and face new challenges successfully. The unity that so greatly strengthened it politically was not a precondition but was fought for in countless, often difficult, negotiations among member states.

Cooperation among nation-states often involves tensions over financial contributions for collective goods, and relations under NATO are no exception. America has always accounted for the largest share of defense spending within the Alliance, so it is not wrong to demand periodically that its European counterparts contribute more. Europe's economies are far stronger now than they were in 1949.

The large U.S. share of the European defense burden dates back to this time. Today, partly rightly so, the United States demands a bigger financial contribution from European members for collective defense. When NATO was founded, the U.S. made a strategic choice that Europe, and particularly Germany, should not be in a position to defend themselves on their own.

To be sure, as one of the front lines during the Cold War, Germany bore a significant burden. Its territory –both West and East – was host to millions of soldiers and thousands of tanks and rockets, all lined up and ready for combat. Most of these soldiers were German, on both sides of the Iron Curtain. But, more than that, it made significant political contributions. In the 1970s, German Chancellor Willy Brandt's policy of Ostpolitik laid the foundation for a European security framework that helped keep the peace until Germany's reunification.

Still, U.S. President Donald Trump's deeply antagonistic stance toward America's NATO allies has led some to call for more distance between Europe and the U.S. They should be careful what they wish for. Europeans do not have a promising historical track record of going it alone in the face of a determined foe.

Though Trump threatens punitive tariffs and demands that European countries increase their defense spending to 2 percent of GDP, he has not followed up his words with action. In this respect, Germany is not so different. Though it declares itself to be a responsible grownup, it has done very little, despite real increases in defense spending since 2013, to improve operational readiness. Indeed, Germany's failure to match deeds with words reflects the country's utter lack of clarity on matters of defense.

Germany is also the target of increasing criticism within NATO itself. Many have come to regard the country's size and political, financial, and economic clout as problematic. For example, in the United Kingdom's Brexit debate, the “Leave” camp wants to escape from a German-dominated Europe, whereas "Remainders" argue that Britain's presence within the EU is needed to check German power.

In fact, neither the UK nor France is in any position to pressure Germany when it comes to charting a course for Europe. The only country with the political and economic clout to do that is the US. The risk, then, is that Trump's anti-German rhetoric will convince Germany that it should distance itself from the transatlantic alliance and put all of its chips on Europe.

Instead of Europe remaining united, pursuing a policy of "equidistance" between the U.S., Russia, and China – as some have proposed – is only likely to divide it further, leaving both Europeans and Germans themselves less secure. The Eastern European countries in NATO and the EU will not entrust their defense to Europeans alone, and particularly not to Germany, which has proven to be an unreliable partner too many times in the past.

Likewise, the notion of "strategic autonomy," currently in vogue in Germany and France, is a recipe for European division, because it implies that there are issues on which the EU might break with the U.S. More European strategic sovereignty is called for, and this comprises far more than the military alone.

However, the only way for Europe to achieve genuine strategic sovereignty is to resolve the tensions over burden-sharing within NATO. Here, Germany could play a decisive role. Instead of increasing its defense spending to 2 percent of GDP, which might worry some of its neighbors, it could invest 1.5 percent in its own forces and offer the remaining 0.5 percent to Eastern European NATO members to spend on defense. This way, Germany would finally back up its words with action and assume a leading role in ensuring Eastern European security.

Three decades after the Cold War, there is no longer a military line running through Germany. But there is a political one, between what is required of Germany militarily and what seems acceptable to German society. One way or another, this line, too, must be erased. Germany has an opportunity and a responsibility both to take care of itself and act as the responsible adult in NATO.

Ultimately, an alliance is only as strong as its members' commitment to it. Now is the time for Germany to show its NATO allies that it is a credible and willing partner and that its foreign and security policies will no longer be guided solely by domestic concerns.