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Shields of the Republic: The Triumph and Peril of America’s Alliances 

Shields of the Republic: The Triumph and Peril of America’s Alliances by Mira Rapp-Hooper. Harvard University Press, 2020, 272 pp.

Shields of the Republic marshals the rich history of US alliances to argue that America’s competitive edge hinges on the strength of old alliances adapted to new challenges. Mira Rapp-Hooper is a Schwarzman Senior Fellow for Asia Studies at the Council on Foreign Relations and a Senior Fellow at the China Center at Yale Law School. Her book is timely as the US pivots its national defense strategy to major-power rivalries and continually weighs the costs and benefits of its global alliances.

Ms. Rapp-Hooper believes that the US can counter Russian subterfuge and Chinese ascendency only if it relies on alliances. Alliances refer to relationships that have been codified in mutual defense treaties, excluding informal alignments (such as the US-Israel relationship) and defense pledges (such as the US-Taiwan pledge). As a tool of statecraft, alliances empower Washington to keep Moscow from infringing on Europe’s political autonomy and Beijing from establishing a closed sphere of influence in Asia. Alarmingly, such adversaries have turned in recent time to “competitive coercion”: nonmilitary and subconventional use of force in limited, obscure, and deniable ways that avoid triggering US defense commitments.

To be sure, these are uneasy times for alliance proponents as the America First movement is once again in vogue. Ms. Rapp-Hooper characterizes this as an era of alliance distrust in which presidential antipathy to defense pacts helps fuel populist belief that alliances are unfairly expensive, entangling, and unnecessary for security. As the US questions its role in the world, our alliance system approaches insolvency—not financially, but in terms of disconnect from origins and fundamental purposes. A historical recounting serves as a reminder that only by pooling resources can allies defend against a rival that might otherwise be able to defeat them individually.

While George Washington is often credited with warning against “entangling alliances” with foreign nations, this warning was actually delivered in Thomas Jefferson’s 1801 inaugural speech. From the birth of our nation to World War I, the US eschewed alliances. Even in the Great War, the US forged European alliances only as an “associated power” rather than as a formal ally. Only in World War II did the US finally pen its first alliances—and only as a tool to further America’s preferred strategy of forward defense, meaning a peacetime alliance system far from the homeland that neutralized threats before they reached our shores. In this way, allied democracies served as America’s front lines, parrying threats before they arrived. Between 1948 and 1955, US leaders extended defensive security guarantees to 23 countries in Europe and Asia. Seventy years later, it was 37 countries.

In the postwar years, the US continued to rely on alliances, but of an entirely novel sort. This new kind of alliance served a grand strategy predicated not on victory in a single conflict (as before) but on maintenance of the balance of power in Europe and Asia. Prior alliances served to win wars; postwar alliances would serve to avert them altogether. US officials’ central worry was that a decimated Europe would easily succumb to Soviet pressure. Washington’s alliance entrepreneurship kicked into overdrive—turning its focus from 1948–50 to Europe and from 1950–52 to Asia. These alliances lowered the cost of military and political action worldwide and fostered the “long peace” between major powers after WWII.

Roughly 75 years after the US forged its first alliance, defense treaties remain vital, but the system and its logics have not been updated for the contemporary world. Ms. Rapp-Hooper asserts that the US must retain but repurpose its alliances to include, for example, new collective defense triggers. Also, the US and its allies must develop thresholds for responding to competitive coercion, such as information warfare and cyberattacks that skirt the terms of current defense pacts.

Of all threats, China receives the most attention in Shields of the Republic. The greatest military risk to American and allied interests in the Pacific is the potential that China succeeds in preventing US military access to and maneuver around the First Island Chain. This would leave US allies undefended and China the sole regional powerbroker. A First Island Chain defense strategy would rely on allies’ geographic positions to restore the military balance that China has upended with its A2/AD activities. This would involve the installation of land- and ship-based missiles, which are controversial among some American allies and would require substantial buy-in to be effective. The US can also counter China with increased US and allied support to Southeast Asian countries that cannot counter maritime and economic coercion on their own. These include allies such as the Philippines and nontreaty partners such as Vietnam.

Of its few weaknesses, Shields of the Republic suffers from an overly ambitious scope, covering all US alliances in Europe and Asia through present day, rather than focusing on a single country or region. Narrowing the scope of the book would enable less superficial topic coverage. In addition, Ms. Rapp-Hooper relies on “counterfactual analysis,” permitting her to prophesize how world events might have transpired differently absent alliances. She maintains that if alliances are serving their defensive, deterrence, and assurance purposes, wars and crises will never erupt, and allies will not defect. Yet she predicts how particular world events might have been negatively altered sans alliances. Unable to isolate a single variable, Ms. Rapp-Hooper admits that counterfactual analysis is an “imperfect technique.” Thus, some of her arguments in favor of alliances are unassailable and flimsy because they are purely hypothetical. Still, the author includes a sufficient amount of empirical data regarding alliance spending and participation to bolster her thesis.

Some look upon the last two decades of foreign policy and wonder why Washington devoted so much effort to wars in the Middle East rather than the rising threats of Russia and China. Ms. Rapp-Hooper saves this quandary for another day and instead focuses on alliances as the only tool of statecraft that will enable the US to maintain dominance over these adversaries.

Capt Matthew H. Ormsbee, USAF

"The views expressed are those of the author(s) and do not reflect the official policy or position of the US government or the Department of Defense."

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