Skip to main content Accessibility help

Arms versus Democratic Allies

  • Matthew Digiuseppe and Paul Poast


In theory, states can gain security by acquiring internal arms or external allies. Yet the empirical literature offers mixed findings: some studies find arms and allies to be substitutes, while others find them to be complements. This article contends that these conflicting findings are due to scholars failing to consider how regime type influences the choice between arms and allies. Since democracies are highly credible allies, states that form alliances with democracies can confidently reduce their internal arms. This is not the case when states form alliances with non-democracies. This study evaluates the argument using data on military expenditures and defense pacts from 1950 to 2001. Taking steps to account for the potentially endogenous relationship between arms and allies, it finds that democratic alliances are associated with lower levels of military spending.



Hide All

Department of Political Science, University of Mississippi (email:; Department of Political Science, University of Chicago (email: Data replication sets are available at and online appendices are available at



Hide All
Allen, Michael A., and DiGiuseppe, Matthew. 2013. Tightening the Belt: Sovereign Debt and Alliance Formation. International Studies Quarterly 57 (4):647659.
Altfeld, Michael. 1984. The Decision to Ally. Western Political Quarterly 37 (4):523544.
Barnett, Michael N., and Levy, Jack S.. 1991. Domestic Sources of Alliances and Alignment: The Case of Egypt, 1962–73. International Organization 45 (3):369395.
Beck, Nathaniel, and Katz, Jonathan. 2011. Modeling Dynamics in Time-Series-Cross-Sectional Political Economy Data. Annual Review of Political Science 14:331352.
Bennett, Scott D. 1997. Democracy, Regime Change, and Rivalry Termination. International Interactions 22 (4):369397.
Benson, Brett V., Meirowitz, Adam, and Ramsay, Kristopher W.. 2014. Inducing Deterrence Through Moral Hazard in Alliance Contracts. Journal of Conflict Resolution 58 (2):307335.
Boef, Suzanna D., and Keele, Luke. 2008. Taking Time Seriously. American Journal of Political Science 52 (1):184200.
Bueno de Mesquita, Bruce, Smith, Alastair, Siverson, Randolph M., and Morrow, James D.. 2003. The Logic of Political Survival. Cambridge, MA: MIT Press.
Bueno de Mesquita, Bruce, Morrow, James D., Siverson, Randolph M., and Smith, Alastair. 1999. An Institutional Explanation of the Democratic Peace. The American Political Science Review 93 (4):791807.
Chen, Baizhu, Feng, Yi, and Masroori, Cyrus. 1996. Collective Action in the Middle East? A Study of Free-Ride in Defense. Journal of Peace Research 33 (3):323339.
Clare, Joe. 2013. The Deterrent Value of Democratic Allies. International Studies Quarterly 57:545555.
Conybeare, John A. C. 1992. A Portfolio Diversification Model of Alliances. Journal of Conflict Resolution 36 (1):5385.
Conybeare, John A. C. 1994. Arms Versus Allies: The Capital Structure of Military Enterprise. Journal of Conflict Resolution 38 (2):215235.
Dai, Xinyuan. 2005. Why Comply? The Domestic Constituency Mechanism. International Organization 59 (2):363398.
Diehl, Paul F. 1994. Substitutes or Complements?: The Effects of Alliances on Military Spending in Major Power Rivalries. International Interactions 19 (3):159176.
Fordham, Benjamin, and Poast, Paul. Forthcoming. All Alliances are Multilateral: Rethinking Alliance Formation. Journal of Conflict Resolution.
Fordham, Benjamin, and Walker, Thomas. 2005. Kantian Liberalism, Regime Type, and Military Resource Allocation: Do Democracies Spend Less? International Studies Quarterly 4 (1):141157.
Gartzke, Erik, and Weisiger, Alex. 2013. Fading Friendships: Alliances, Affinities and the Activation of International Identities. British Journal of Political Science 43 (1):2552.
Gartzke, Erik, and Gleditsch, Kristian S.. 2004. Why Democracies May Actually be Less Reliable Allies. American Journal of Political Science 48 (4):775795.
Gaubatz, Kurt T. 1996. Democratic States and Commitment in International Relations. International Organization 50 (1):109139.
Gibler, Douglas. 2008. The Costs of Reneging: Reputation and Alliance Formation. Journal of Conflict Resolution 52 (3):426454.
Gibler, Douglas, and Wolford, Scott. 2006. Alliances, Then Democracy: An Examination of the Relationship Between Regime Type and Alliance Formation. Journal of Conflict Resolution 50 (1):129153.
Goldsmith, Benjamin. 2007. Defense Effort and Institutional Theories of Democratic Peace and Victory: Why Try Harder? Security Studies 16 (2):189222.
Greene, William H. 2000. Econometric Analysis, 4th edition, New York: Prentice-Hall.
Guzman, Andrew T. 2009. How International Law Works: A Response to Commentators. International Theory 1 (2):335343.
Hart, Robert A. Jr., and Reed, William. 1999. Selection Effects and Dispute Escalation: Democracy and Status Quo Evaluations. International Interactions 25 (3):243263.
Horowitz, Michael C., Simpson, Erin M., and Stam, Alan C.. 2011. Domestic Institutions and Wartime Casualties. International Studies Quarterly 55 (4):909936.
Horowitz, Michael C., Poast, Paul, and Stam, Alan C.. Forthcoming. Domestic Signaling of Commitment Credibility: Military Recruitment and Alliance Formation. Journal of Conflict Resolution.
Johnson, Jesse, Leeds, Brett Ashley, and Wu, Ahra. 2015. Capability, Credibility, and the Extended General Deterrence. International Interactions 41 (2):309336.
Keele, Luke, and Kelly, Nathan J.. 2006. Dynamic Models for Dynamic Theories: The Ins and Outs of Lagged Dependent Variables. Political Analysis 14:186205.
Keshk, Omar, Pollins, Brian M., and Reuveny, Raphael. 2004. Trade Still Follows the Flag: The Primacy of Politics in a Simultaneous Model of Interdependence and Armed Conflict. Journal of Politics 66 (4):11551179.
Kimball, Anessa L. 2010. Political Survival, Policy Distribution, and Alliance Formation. Journal of Peace Research 47 (4):407419.
Koremenos, Barbara, Lipson, Charles, and Snidal, Duncan. 2001. The Rational Design of International Institutions. International Organization 55 (4):761799.
Koyck, Leendert M. 1954. Distributed Lags and Investment Analysis, Vol. 4. Amsterdam: North-Holland Publishing Company.
Kydd, Andrew. 2009. Reputation and Cooperation: Guzman on International Law. International Theory 1 (2):295305.
Lai, Brian, and Reiter, Dan. 2000. Democracy, Political Similarity, and International Alliances, 1816–1992. Journal of Conflict Resolution 44 (2):203227.
Leeds, Brett Ashley. 1999. Domestic Political Institutions, Credible Commitments, and International Cooperation. American Journal of Political Science 43 (4):9791002.
Leeds, Brett Ashley. 2003. Alliance Reliability in Times of War: Explaining State Decisions to Violate Treaties. International Organization 57 (4):801827.
Leeds, Brett Ashley, and Savun, Burcu. 2007. Terminating Alliances: Why do States Abrogate Agreements? Journal of Politics 69 (4):11181132.
Leeds, Brett Ashley, Ritter, Jeffrey M., Mitchell, Sara L., and Long, Andrew G.. 2002. Alliance Treaty Obligations and Provisions, 1815–1944. International Interactions 28 (3):237260.
Leeds, Brett Ashley, Mattes, Michaela, and Vogel, Jeremy S.. 2009. Interests, Institutions, and the Reliability of International Commitments. American Journal of Political Science 53 (2):461476.
Leeds, Brett Ashley, and Anac, Sezi. 2005. Alliance Institutionalization and Alliance Performance. International Interactions 31 (1):183202.
Levendusky, Matthew S., and Horowitz, Michael C.. 2012. When Backing Down is the Right Decision: Partisanship, New Information, and Audience Costs. The Journal of Politics 74 (2):323338.
Levy, Jack S., McKoy, Michael K., Poast, Paul, and PR Wallace, Geoffrey. 2015. Backing Out or Backing In? Commitment and Consistency in Audience Costs Theory. American Journal of Political Science 59 (4):9881001.
Marshall, Monty G., Jaggers, Keith, and Gurr, Ted. 2010. Polity IV Project: Data Users Manual. Available at, accessed 18 May 2016.
Martin, Lisa L. 2000. Democratic Commitments: Legislatures and International Cooperation. Princeton, NJ: Princeton University Press.
Mattes, Michaela. 2012a. Democratic Reliability, Precommitment of Successor Governments, and the Choice of Alliance Commitment. International Organization 66 (1):153172.
Mattes, Michaela. 2012b. Reputation, Symmetry, and Alliance Design. International Organization 66 (4):679707.
Mattes, Michaela, Leeds, Brett Ashley, and Carroll, Royce. 2015. Leadership Turnover and Foreign Policy Change: Societal Interests, Domestic Institutions, and Voting in the United Nations. International Studies Quarterly 59 (2):280290.
McGillivray, Fiona, and Smith, Alastair. 2004. The Impact of Leadership Turnover on Trading Relations Between States. International Organization 58 (3):567600.
McGillivray, Fiona, and Smith, Alastair. 2008. Punishing the Prince: A Theory of Interstate Relations, Political Institutions, and Leader Change. Princeton, NJ: Princeton University Press.
Michon, Georges. 1929. The Franco-Russian Alliance, 1891–1917. Sydney: Allen & Unwin.
Morgan, T. Clifton, and Palmer, Glenn. 2006. A Theory of Foreign Policy. Princeton, NJ: Princeton University Press.
Morgenthau, Hans. 1948. Politics Among Nations. The Struggle for Power and Peace. New York: Alfred A. Knopf.
Morrow, James D. 1991. Alliances and Asymmetry: An Alternative to the Capability Aggregation Model of Alliances. American Journal of Political Science 35 (4):904933.
Morrow, James D. 1993. Arms Versus Allies: Trade-Offs in the Search for Security. International Organization 47 (2):207233.
Morrow, James D. 1994. Alliances, Credibility, and Peacetime Costs. Journal of Conflict Resolution 38 (2):270297.
Most, Benjamin A., and Siverson, Randolph M.. 1987. Substituting Arms and Alliances, 1870-1914: An Exploration in Comparative Foreign Policy. In New Directions in the Study of Foreign Policy, edited by C. F. Hermann, C. W. Kegley and J. Rosenau. Boston, MA: Allen and Unwin.
Murdie, Amanda, and Peksen, Dursun. 2014. The Impact of Human Rights INGO Shaming on Humanitarian Intervention. Journal of Politics 76 (1):215228.
Nordhaus, William, Oneal, John R., and Russett, Bruce. 2012. The Effects of International Security Environment on National Military Expenditures: A Multi-Country Study. International Organization 66 (3):491513.
Nordhaus, William, and Tobin, James. 1972. Is Growth Obsolete? In Economic Research: Retrospect and Prospect Vol 5: Economic Growth, edited by William Nordhaus and James Tobin, 180. Cambridge, MA: NBER.
Olson, Mancur, and Zeckhauser, Richard. 1966. An Economic Theory of Alliances. The Review of Economics and Statistics 48 (3):266279.
Plumper, Thomas, and Neumayer, Eric. 2015. Free-Riding in Alliances: Testing an Old Theory with a New Method. Conflict Management and Peace Science 32 (3):247268.
Poast, Paul. 2012. Does Issue Linkage Work? Evidence from European Alliance Negotiations, 1860 to 1945. International Organization 66 (2):277310.
Poast, Paul. 2013. Can Issue Linkage Improve Treaty Credibility? Buffer State Alliances as a Hard Case. Journal of Conflict Resolution 57 (5):739764.
Reed, William. 1997. Alliance Duration and Democracy: An Extension and Cross-Validation of ‘Democratic States and Commitment in International Relations’. American Journal of Political Science 41 (3):10721078.
Reiter, Dani, Stam, Alan, and Downes, Alexander B.. 2009. Another Skirmish in the Battle over Democracies and War. International Security 34 (2):194204.
Reiter, Dani, and Stam, Alan C.. 2002. Democracies at War. Princeton, NJ: Princeton University Press.
Roodman, Dani. 2011. Estimating Fully Observed Recursive Mixed-Process Models with Cmp. Stata Journal 11 (3):159206.
Schultz, Kenneth A. 2001. Democracy and Coercive Diplomacy, Vol. 76. Cambridge: Cambridge University Press.
Schultz, Kenneth A., and Weingast, Barry. 2003. The Democratic Advantage: The Institutional Sources of International Competition. International Organization 57 (1):342.
Smith, Alastair. 1998. International Crises and Domestic Politics. American Political Science Review 92 (3):623638.
Snyder, Glenn H. 1984. The Security Dilemma in Alliance Politics. World Politics 36 (4):461495.
Sorokin, Gerald L. 1994. Arms, Alliances, and Security Tradeoffs in Enduring Rivalries. International Studies Quarterly 38:421446.
Thompson, William R. 2001. Identifying Rivals and Rivalries in World Politics. International Studies Quarterly 45 (4):557586.
Weeks, Jessica. 2008. Autocratic Audience Costs: Regime Type and Signaling Resolve. International Organization 62 (1):3564.
Williams, Laron K., and Whitten, Guy D.. 2012. But Wait, There’s More! Maximizing Substantive Inferences from TSCS Models. Journal of Politics 74 (3):685693.


Type Description Title
Supplementary materials

Digiuseppe and Poast Dataset

Supplementary materials

Digiuseppe and Poast supplementary material

 PDF (186 KB)
186 KB

Arms versus Democratic Allies

  • Matthew Digiuseppe and Paul Poast


Altmetric attention score

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed