Even as NATO heads of state prepare to discuss Russia and global terror at their annual summit this month, a deeper issue is haunting America’s allies around the globe: their relative military and economic decline over the past two decades — and the increasingly sharp geopolitical challenges this poses for the United States.

The Trump administration is nearing its 100-day marker, a useful milestone for reflecting upon what the president has done and where he is going. There is certainly much to consider: President Donald Trump came to Washington pledging to break dramatically with American foreign policy as we have known it for decades, and his early presidency has been a whirlwind of activity, controversy, and chaos. So what do we know about foreign policy in the Trump era? There are six key takeaways so far.

America is an exceptional nation, but not when it comes to the wave of nationalism sweeping the globe. Across multiple continents, leaders and polities are pushing back against globalization and integration; they are reasserting national sovereignty as a bulwark against international tumult. In the United States, this nationalist resurgence has manifested in a sharp and potentially existential challenge to the internationalist project that has animated U.S. grand strategy since World War II.

“The Trump team certainly has opened the aperture,” former Pentagon adviser Hal Brands, now at Johns Hopkins’ School of Advanced International Studies in the District, told The Washington Times in March

Hal Brands, a professor at the School of Advanced International Studies, says that may reflect a shift in which of his competing advisers Trump is listening to.

As a result of the U.S. airstrikes against the Syrian military last week, we are all about to learn a great deal. It is, surely, too soon to know precisely what impact the strikes ordered by President Donald Trump will have on the regime and where the Syrian civil war is heading. This is largely because key players including Syrian President Bashar al-Assad, Russia, Iran and the Syrian opposition -- not to mention the U.S. -- are still plotting their next moves.