One of the most important outcomes of the U.S. presidential race may be how it affects the United States’ relationship with Europe. Donald Trump has clearly stated that he wants Europe to pay more of the cost of NATO – a perennial point of contention between the U.S. and the alliance. Either way, the crux of the issue is the strategic relationship between the United States and Europe.
The U.S. has gone to war – or near to war – three times with European powers that had sought to take control of the Continent. The first occurred in 1917, when the United States deployed forces to France to fight Germany. The intervention was ostensibly triggered by German submarines that had sunk British and French ships before turning on U.S. vessels en route to Europe. But it was more fundamentally driven by the fact that U.S. trade with Europe had continued profitably through the first phase of World War I; the German attempt to attack shipping was an attempt to cut the supply line between Britain and the United States. German forces were being weakened on land, so Berlin hoped that intercepting ships from the U.S. would hurt the British war effort and, in turn, relieve its troops.
For Washington, it was more than a matter of losing vessels. The U.S. and Europe formed the economic heart of the world. Whereas the French and the British were fighting for their lives, the Americans were fighting to preserve the economic relationship that was the backbone of the U.S. economy.
This defined the U.S. strategy. The United States was safe from land invasion – neither Canada nor Mexico was a threat – so the only possible avenue for invasion was the sea. So in addition to the threat to its trade, the U.S. was concerned that another power would take control of the Atlantic and stage an amphibious assault. Washington’s strategy was to break Germany’s land power and prevent its navy from securing the Atlantic. This could be achieved only through an alliance with Western Europe on land and sea because their defeat would leave the U.S. vulnerable to Germany.
The U.S. would intervene in Europe a second time in World War II, which left the United States in virtually the same position. Washington was compelled to defend the Atlantic and prevent the fall of Western Europe. More specifically, the U.S. feared that Germany would invade and occupy Britain and take control of its massive naval fleet. This was a mortal threat to U.S. trade and national security. Thus it pursued the same strategy it did in WWI, providing massive naval aid to London to keep the Germans from gaining control of the Atlantic.
The key difference, of course, is that the U.S. also faced Japan in the Pacific Ocean. For Washington, a simultaneous threat from the Atlantic and Pacific oceans was the worst-case scenario. The Pacific War was a naval war.
The third intervention took place during the Cold War, with the U.S. maintaining lines across the Atlantic to supply Western Europe and NATO forces engaged with the Soviet Union. Only this time both sides held nuclear weapons, so any hot war would be an air-land war. American defense of the sea was fought from the land and air but was still, in principle, a naval war.
The larger point is that these wars were fought in the context of an alliance, and that U.S. strategy has been largely unchanged for over a century. In accordance with that strategy, Washington expects to fight a naval war and supply U.S. forces, while buttressing its assets with an alliance drawn from land forces on the key land battlefields.
In this sense, NATO as an organization is not necessary for a U.S. war in Europe. But the troops it could supply would sure be welcome. And it must be remembered that the U.S. still needs trade – and trade with Europe is most important. Keeping naval lines open was the key to U.S. wars in the 20th century. This remains the case now and will continue to do so in the future.