U.S. Trans-Pacific and Trans-Atlantic Alliances: A Comparison

U.S. Trans-Pacific and Trans-Atlantic Alliances: A Comparison

The United States has an extensive global network of security partnerships, the most important of which are in East Asia and Europe. U.S. allies in both regions are under increasing pressure from China and Russia, while President Trump’s contemptuous attitude toward them incites additional uncertainty about the reliability of the U.S. security umbrella. In particular, East Asian allies are anxious about Trump’s fluctuating relationship with North Korea’s Kim Jong-un, and are waiting to see the impact of Kim’s nuclear capability on U.S. military activity in the Korean Peninsula. Given recent concerns voiced by U.S. allies, it is crucial to evaluate the circumstantial similarities and differences between U.S. trans-Pacific and trans-Atlantic alliances in order to assess the overarching implications for the U.S. military alliance network going forward.


To date, East Asian and European allies have enjoyed relative safety under the patronage of the United States. Through formal alliance agreements, the United States has provided guarantees of military protection, which have deterred states from waging war against U.S. allies in situations where the United States had applicable defense obligations. Granted, states whose interests align closely with the United States have been targets of large-scale military aggression, but it is hard to think of a case in which a formal defense pact had been already signed and in which the U.S. defense obligation was actually applicable (most U.S. alliance agreements have conditions for fulfillment). The U.S.-South Korean alliance, for instance, was signed after the Korean War. The First Taiwan Strait Crisis began before the United States signed its mutual defense treaty with Taiwan in 1954. South Vietnam was never a formal ally of the United States because of the terms of the 1954 Geneva Agreements, although Washington did apply its Southeast Asia Treaty Organization (SEATO) defense obligations to Saigon – despite it not belonging to SEATO. In other cases, such as the 1958 Taiwan Strait Crisis or Pakistan’s wars with India, the preconditions for U.S. military intervention exempted Washington from coming to the aid of its partners.

U.S. allies in both East Asia and Europe have illiberal, militarized rivals who engage in aggressive tactics that nevertheless aim to avoid triggering military retaliation. China and Russia challenge or circumvent U.S. extended deterrence with gray-zone tactics to avoid international criticism and U.S. military intervention. Russia’s Little Green Men and China’s Little Blue Men – military forces deployed undercover in Ukraine and the South and East China Seas, respectively – come to mind. China, in particular, has used maritime militia and civilian vessels effectively to advance its maritime and territorial claims. These achievements give U.S. allies reason to worry about their security, even with America’s strong record of deterring armed aggression.

Finally, both East Asian and European allies are concerned about Trump’s rhetoric and hostility toward long-standing alliances. They share acute concerns about U.S. pressure for burden-sharing in terms of defense spending and host nation support. According to Trump, allies should be prepared “to protect themselves or ... pay” the United States. Although Americans have long harbored a certain skepticism concerning the benefits of overseas alliances, U.S. allies fear that Trump will prioritize short-term gains over the long-term health of his country’s security partnerships. 


U.S. alliances in East Asia are bilateral, while those in Europe take the form of a large multilateral military alliance, the North Atlantic Treaty Organization (NATO). Although the United States is clearly a dominant military patron in both regions, mutual defense obligations between non-U.S. participants in NATO are not inconsequential. If European allies of the United States increased defense spending or intra-European military cooperation, they could balance against Russia without relying on the United States. The United Kingdom and France are particularly important as they possess nuclear arsenals, but other European powers can also bring substantial military capabilities. For example, according to estimates from the Stockholm International Peace Research Institute, if Germany had spent the same percentage of its GDP on its military as Russia did in 2017, Germany's military budget alone would have been 2.4 times that of Russia’s. In East Asia, however, China’s neighbors are militarily outclassed. Japan and South Korea lack nuclear weapons, and their combined defense expenditures are dwarfed by China’s.

The two regions also differ in their proximate threats. U.S. allies in Asia face China’s military challenges at sea over maritime territorial disputes, with recent Sino-Japanese frictions over the Senkaku/ Diaoyu Islands taking center stage. Sino-South Korean frictions in the Yellow Sea remain relatively calm but could escalate quickly if either China or South Korea decides to stop their efforts to subdue the dispute.  In Europe, meanwhile, Russia’s land-based military threats loom large. Generally, maritime disputes are less threatening than land disputes because maritime borders and territories are typically far removed from claimants’ metropolitan areas. This, however, could expedite dispute initiation and escalation should the disputants believe that a maritime conflict can be easily contained.

Finally, with no European equivalent of North Korea, America’s European allies do not harbor the same uncertainties that confront their East Asian counterparts. North Korea’s nuclear capabilities are a wild card for neighboring U.S allies. Japan, in particular, has expressed anxiety about the rapid improvement of North Korea’s nuclear and missile arsenals amid Trump's negotiations with Kim. Meanwhile, recent developments are not as concerning for South Korea, which had already been militarily vulnerable to North Korean attacks. Seoul’s immediate priority is to avoid a war on the Korean Peninsula, and a North Korean nuclear arsenal may be less troublesome for South Koreans as it reduces the likelihood of the United States attacking North Korea. Despite all the problems Pyongyang presents to the region, it is also important to acknowledge that North Korea has provided a politically convenient justification for sustaining U.S. alliances in Asia. 


This comparative analysis of U.S. security alliances in East Asia and Europe offers a few key insights. First, given recent Chinese and Russian attempts to erode U.S. extended deterrence, Washington’s East Asian and European allies should provide each other with diplomatic support in the face of China’s and Russia’s subversion of the territorial status quo. Moreover, countries like Japan, South Korea, Germany, and France should be prepared to oppose Trump administration policies signaling disregard for foreign partners,  as seen in the White House’s unilateral changes in posture toward North Korea and Iran, and the U.S. withdrawal from the Trans-Pacific Partnership.

Because of the differing political and military situations in the two regions, it seems more important for the United States to assist East Asian allies than European allies, especially for long-term alliance management. As discussed earlier, the United States plays a more crucial role in maintaining the balance of power in East Asia than in Europe. Furthermore, U.S. retrenchment from East Asia will also mean reduced U.S. influence in the broader Asia-Pacific or Indo-Pacific region, whose economic importance continues to grow. As China’s military capabilities increase, the United States must prevent a future in which Asian states are coerced into aligning with China.

In Asia, U.S. allies face two main contenders: North Korea and China. The two are inextricably linked. Although the North Korean threat is more immediate, U.S. decision-making regarding North Korea – for example, about the future status of U.S. forces on the peninsula – will have direct implications for Washington's dealings with Beijing. Given that the threat from North Korea has been the central rationale for the U.S. military presence in South Korea, China’s best bet for reducing American involvement in East Asia currently lies in advancing inter-Korean diplomacy and peace. Additionally, European allies should pay closer attention to developments in Asia, not only because the two regions are economically interdependent, but also because events in Asia have significant impact on European security. The Obama administration’s rebalance to Asia may have been worrisome for Europe, but Trump has taken Asian and European allies’ anxiety to a whole new level.


Dr. Tongfi Kim is an assistant professor of international affairs at Vesalius College and a senior researcher at the KF-VUB Korea Chair in Brussels, Belgium. He specializes in military alliances, and is author of The Supply Side of Security: A Market Theory of Military Alliances.