*This lit review is part of a broader project that will be uploaded upon completion
The literature on alliances has focused largely on answering questions concerning alliance formation, balancing versus bandwagoning, and the effectiveness of defensive alliances as deterrents. Kenneth Waltz’s and Stephen Walt’s work on balance of power theory and balance of threat theory, respectively, have contributed enormously to our understanding of these questions. However, because these realist scholars assume that alliances will always be short-lived, as they believe that alliances are constantly changing to adjust to shifting power distributions, their theories devote little time to investigating how alliances are organized. Liberal scholars have attempted to expand upon the alliance literature by elucidating the ways in which states create interdependent alliance networks, and G. John Ikenberry, in particular, has significantly added to our understanding of the post-war liberal order. However, most liberal analyses tend to focus on broader systems of international institutionalization and thus view military alliances as simply a part of a larger whole, not as major institutions in their own right. More recent studies by Lake and Weber have partially rectified this problem by examining why states choose different defensive arrangements such as empires, confederations, and alliances. But, their work fails to acknowledge the wide degree of variation within alliances themselves. Thus, little work exists to explain alliance organization and its impact on domestic structures within individual states. And while we have a copious number of theories to explain when and why states choose to balance against threats, there is very little formal theory dedicated to explaining the ways in which they choose to balance.
Despite the relative dearth of research on alliance organization, recent research has demonstrated a move toward questions concerning the institutionalization of alliances and the organizational principles that undergird large alliance networks like NATO. One strand of literature examines the difference between short-lived coalitions and enduring alliances. Kirsten Rafferty, for example, has investigated why certain alliance networks remain durable decades after their initial founding while others quickly collapse. She argues that shared norms, strong institutionalization of alliances, and shared security and non-security interests all contribute to alliance durability and adaptability. Patricia Weitsman has further contributed to our understanding of alliance durability and effectiveness by investigating the organizational differences between institutionalized military alliances and ad hoc military coalitions. She contends that although alliances are better integrated and possess more well-developed institutions, their egalitarian structures, often designed during times of peace, are often inefficient, redundant, and poorly equipped to engage in high-intensity military conflicts. Coalitions, by contrast, are far more flexible and tailored for specific conflicts, but they lack the institutional durability of alliances.
Another segment of the literature has attempted to explain alliance organization from a structural level, focusing on systemic power distributions and balance of threat theory to explain the variation in alliances. One example of this is Michaela Mattes’ work on identifying the ways in which power distribution and state credibility impact alliances. Mattes argues that unreliable allies that are in rough parity with one another attempt to strongly institutionalize alliances to prevent abandonment. Unequal alliances with reliable members, by contrast, tend to be less institutionalized because there is little of risk of reliable members shirking their duties and, even if there were such a risk, unequal power distributions within the alliance would prevent the weak state from institutionally constraining the more powerful state. Unfortunately, Mattes examines only bilateral alliance networks, and thus her theory may not apply to the many multilateral alliance systems found around the world. Indeed, she explicitly states that institutionalization pressures will likely be lower in multilateral alliances. However, other scholars have used structural level factors to explain why states sometimes choose multilateral alliances but other times prefer bilateral alliances. Steve Weber’s work on NATO is an example of this, as it attempts to explain the creation of a multilateral NATO by arguing that institutional efficiency was the primary motivation for creating a multilateral alliance. In other words, a multilateral mutual defense pact more effectively allowed resources to be pooled against the perceived Soviet threat. In Asia, by contrast, the relatively weak U.S. allies were too ineffective to warrant the creation of a highly institutionalized and interdependent alliance system that risked constraining U.S. freedom of action. The U.S., therefore, chose to create a bilateral alliance network instead.
The final major strand of the literature on alliance organization has focused on the ways in which domestic factors shape military alliances. Ryan Dudley, for example, has examined the impact of domestic variables on alliance formation and contends that because states can only reliably effect domestic issues, exogenous pressures at the systemic level play a smaller role in shaping alliance formation. While his work provides few specific insights into the development of institutions within alliances, Dudley convincingly argues that endogenous domestic variables play a larger role in explaining alliance organization and durability than exogenous factors within the international system. Michaela Mattes has done further work in this vein and has specified the relationship between regime type and alliance organization. She argues that democracies tend to favor more strongly institutionalized military alliances because more stringent institutional constraints, by locking in commitments, allow the domestic party in power to limit the ability of successor governments to adopt alternate foreign policies and military alignments. Anessa Kimball has also sought to understand the link between domestic pressures and alliance formation, suggesting that alliances are often used as means of “contracting out security” to solve the distributional dilemma. Instead of using alliances to balance external threats, then, Kimball suggests that they primarily serve as a means for states to devote greater resources to domestic programs like welfare and education while their allies effectively subsidize defense spending. Her findings are broadly similar to those of Barnett and Levy, two scholars who have also examined the relationship between the “guns and butter tradeoff” and alliance formation. Finally, Horowitz, Poast, and Stam have conducted fascinating research on the relationship between states’ domestic military policies and their propensity to ally. Specifically, they suggest that states that clearly signal a commitment to military strength tend to find allies more easily, as their military investment signals a credible commitment to maintaining a military force strong enough to positively augment the overall power of the alliance.
Despite adopting multiple approaches to studying alliance organization, all of the existing literature views alliances and their institutional structures only as dependent variables. Questions about the impact of alliances on member states’ domestic organizations are almost entirely ignored in academic circles of international relations, and that represents a major lacuna. The one exception to this is the literature on alliance membership and its impact on domestic regime type; the relationship between NATO membership and democratization has received significant attention in academic international relations. Beyond the question of democratization, though, there is virtually no academic literature addressing the manners in which alliance membership shapes domestic institutions within a country.
The reason for this paucity of research is partially explained by the fact that, at least anecdotally, military alliances do not seem to significantly impact domestic state institutions and organizations. However, this view ignores a significant caveat: the organization of countries’ armed forces. The idea that alliance membership necessitates some degree of military standardization is hardly controversial within either academic or public policy circles. Indeed, much of the research on alliance organization highlighted above is predicated on the explicit assumption that alliances force military institutionalization and coordination. Nevertheless, there is, as far as I can tell, no formal academic work examining the ways in which alliances shape domestic military procurement and organization. Public policy think tanks have partially ameliorated this gap in the literature by producing significant amounts of research on the kinds of military procurement and organizational doctrines that should be pursued by states in particular alliance networks. Unfortunately, this research tends to be ad hoc and focused on individual states or alliance systems. Moreover, think tank research is usually normative and prescriptive, not descriptive and predictive. Thus, these policy papers and monographs generally fail to offer a broader theoretical grounding with which to analyze the impact of alliances on domestic military organization.
The lack of any formal theory illuminating the linkages between alliance institutions and domestic military organization is troubling, and further research in this area would be valuable for policymakers and academics alike. First, specifying the ways in which alliances shape member states’ militaries would allow scholars to better understand how alliance membership can constrain states’ foreign policies and hard power capabilities. This knowledge would be useful because it could help generate more specific theories of alliance formation and organization. It might also have applications in other subfields of international relations and could expand our understanding of issues ranging from conventional military effectiveness to nuclear proliferation and arms racing. Second, this area of research could be beneficial for policymakers considering the possible second-order effects of joining an alliance. Third, understanding the relationship between alliance membership and military organization could help resolve increasingly contentious debates over NATO spending levels because, if it is the case that membership results in more efficiently designed and mutually-supportive militaries among member states, absolute spending levels might be less important than logistical and organizational questions. In other words, lower spending levels might simply be the product of more efficient intra-alliance military coordination and not, as some right-leaning politicians suggest, self-interested free-riding.
Much of the work examined above provides useful methodological and organizational tools for examining the relationship between alliance organization and domestic military organization. For example, Weitsman’s work comparing alliances and coalitions suggests that alliance membership might actually generate defense redundancies that lead to less efficient distributions of military capabilities within an alliance. Horowitz, Poast, and Stam’s work suggests the opposite might be true, as it links effective domestic military organization with alliance membership. Weber’s research also has interesting implications for military specialization because it suggests the multilateral alliances, as a result of their ability to harness institutional efficiency effects, would likely yield more specialized forces than those found among states in bilateral alliances. In short, despite the lack of meaningful analysis on the interaction between alliance organization and military specialization, much of the existing scholarship on alliance theory could easily be mined to develop theories and empirical tests of these interesting research questions. Therefore, scholars interested in questions broadly related to the intersection of alliance theory and domestic military organization should be able to make significant headway simply by retooling much of the existing literature on military alliances.
 See, for example, Jessie C. Johnson and Brett Ashley Leeds, “Defense Pacts: A Prescription for Peace,” Foreign Policy Analysis 7, no. 1 (January 2011), 45-65; Anessa L. Kimball, “Alliance Formation and Conflict Initiation: The Missing Link,” Journal of Peace Research 43, no. 4 (2006), 371-389; and Randall Schweller, “Bandwagoning for Profit: Bringing the Revisionist State Back In,” International Security 19, no. 1 (Summer 1994), 72-107.
 Stephen M. Walt, The Origins of Alliances (Ithaca, NY: Cornell University Press, 1987) and Kenneth Waltz, Theory of International Politics (Reading, MA: Addison-Wesley Pub. Co., 1979).
 Though not associated with the Liberal School, Brandon J. Kinne, “Network Dynamics and the Evolution of International Cooperation,” American Political Science Review 107, no. 4 (2013), 766-785 provides an excellent analysis of the influence of network dynamics on military cooperation.
 G. John Ikenberry, After Victory: Institutions, Strategic Restraint, and the Rebuilding of Order after Major War (Princeton, NJ: Princeton University Press, 2001) and G. John. Ikenberry, Liberal Leviathan: The Origins, Crisis, and Transformation of the American World Order (Princeton, NJ: Princeton University Press, 2011).
 David A. Lake, Hierarchy in International Relations (Ithaca, NY: Cornell University Press, 2009) and Katja Weber, “Hierarchy Amidst Anarchy: A Transaction Costs Approach to International Security Cooperation,” International Studies Quarterly 41, no. 2 (1997), 321–40.
 Kirsten Rafferty, “An institutionalist reinterpretation of Cold War alliance systems: Insights for alliance theory,” Canadian Journal of Political Science 36, no. 2 (2003), 341-362.
 Patricia Weitsman, Waging War: Alliances, Coalitions, and Institutions of Interstate Violence (Palo Alto, CA: Stanford University Press, 2014) and Patricia Weitsman, “Wartime Alliances versus Coalition Warfare: How Institutional Structure Matters in the Multilateral Prosecution of Wars,” Strategic Studies Quarterly 4, no. 2 (2010), 113-136.
 For an explanation of balance of threat theory, see Walt, 1987.
 Michaela Mattes, “Reputation, Symmetry, and Alliance Design,” International Organization 66, no. 4 (2012), 679-707.
 Ibid., 691.
 Steve Weber, “Shaping the postwar balance of power: Multilateralism in NATO,” International Organization 46, no. 3, 634–680.
 Ryan W. Dudley, “It Takes Two To Tango: An Endogenous Theory of Bilateral Military Alliances” PhD. dissertation, University of California Davis, 2010.
 Michaela Mattes, “Democratic Reliability, Precommitment of Successor Governments, and the Choice of Alliance Commitment,” International Organization 66, no. 1 (2012), 153-177.
 Anessa L. Kimball, “Political survival, policy distribution, and alliance formation,” Journal of Peace Research 47, no. 4 (2010), 407-419.
 Michael N. Barnett and Jack S. Levy, “Domestic sources of alliances and alignments: The case of Egypt, 1962–73,” International Organization 45, no. 3 (1991), 369–395.
 Michael C. Horowitz, Paul Poast, and Allan C. Stam, “Domestic Signaling of Commitment Credibility: Military Recruitment and Alliance Formation,” Journal of Conflict Resolution 1, no. 29 (2015), 1-29.
 For examples, see John C. Pevehouse, Democracy From Above: Regional Organizations and Democratization (Cambridge, U.K: Cambridge University Press, 2005) and Alexandra Gheciu, NATO in the New Europe: The Politics of International Socialization after the Cold War (Palo Alto, CA: Stanford University Press, 2005).
 There are too many examples to exhaustively cite. For examples, though, see CSIS’ “Federated Defense Project” and Andrew Davies and Christopher Cowan, “Australia and Canada: different boats for different folks,” ASPI, December 21, 2016, https://www.aspistrategist.org.au/australia-canada-different-boats-different-folks/.
Barnett, Michael N. and Jack S. Levy. “Domestic sources of alliances and alignments: The case of Egypt, 1962–73,” International Organization 45, no. 3 (1991), 369–395.
Davies, Andrew and Christopher Cowan. “Australia and Canada: different boats for different folks.” ASPI. December 21, 2016. https://www.aspistrategist.org.au/australia-canada-different-boats-different-folks/.
Dudley, Ryan W. “It Takes Two To Tango: An Endogenous Theory of Bilateral Military Alliances.” PhD. dissertation, University of California Davis, 2010.
Gheciu, Alexandra. 2005. NATO in the New Europe: The Politics of International Socialization after the Cold War. Palo Alto, CA: Stanford University Press.
Horowitz, Michael C., Paul Poast, and Allan C. Stam. “Domestic Signaling of Commitment Credibility: Military Recruitment and Alliance Formation.” Journal of Conflict Resolution 1, no. 29 (2015), 1-29.
Ikenberry, G. John. 2001. After Victory: Institutions, Strategic Restraint, and the Rebuilding of Order after Major War. Princeton, NJ: Princeton University Press.
Ikenberry, G. John. 2011. Liberal Leviathan: The Origins, Crisis, and Transformation of the American World Order. Princeton, NJ: Princeton University Press.
Johnson Jessie C. and Brett Ashley Leeds. “Defense Pacts: A Prescription for Peace.” Foreign Policy Analysis 7, no. 1 (January 2011), 45-65.
Kimball, Anessa L. “Alliance Formation and Conflict Initiation: The Missing Link.” Journal of Peace Research 43, no. 4 (2006), 371-389.
Kimball, Anessa L. “Political survival, policy distribution, and alliance formation.” Journal of Peace Research 47, no. 4 (2010), 407-419.
Kinne, Brandon J. “Network Dynamics and the Evolution of International Cooperation.” American Political Science Review 107, no. 4 (2013), 766-785.
Lake, David A. 2009. Hierarchy in International Relations. Ithaca, NY: Cornell University Press.
Mattes, Michaela. “Democratic Reliability, Precommitment of Successor Governments, and the Choice of Alliance Commitment.” International Organization 66, no. 1 (2012), 153-177.
Mattes, Michaela. “Reputation, Symmetry, and Alliance Design.” International Organization 66, no. 4 (2012), 679-707.
Pevehouse, John C. 2005. Democracy From Above: Regional Organizations and Democratization. Cambridge, U.K: Cambridge University Press.
Rafferty, Kirsten. “An institutionalist reinterpretation of Cold War alliance systems: Insights for alliance theory.” Canadian Journal of Political Science 36, no. 2 (2003), 341-362.
Schweller, Randall. “Bandwagoning for Profit: Bringing the Revisionist State Back In.” International Security 19, no. 1 (Summer 1994), 72-107.
Walt, Stephen M. 1987. The Origins of Alliances. Ithaca, NY: Cornell University Press.
Waltz, Kenneth. 1979. Theory of International Politics. Reading, MA: Addison-Wesley Pub. Co.
Weber, Katja. “Hierarchy Amidst Anarchy: A Transaction Costs Approach to International Security Cooperation.” International Studies Quarterly 41, no. 2 (1997), 321–40.
Weber, Steve. “Shaping the postwar balance of power: Multilateralism in NATO.” International Organization 46, no. 3, 634–680.
Weitsman, Patricia. “Wartime Alliances versus Coalition Warfare: How Institutional Structure Matters in the Multilateral Prosecution of Wars.” Strategic Studies Quarterly 4, no. 2 (2010), 113-136.
Weitsman, Patricia. 2014. Waging War: Alliances, Coalitions, and Institutions of Interstate Violence. Palo Alto, CA: Stanford University Press.