Despite widespread concern over heated diplomatic debates and growing interest in public diplomacy, it is still incompletely understood what type of message is more effective for gaining support from foreign public, or the international society, in situations where disputing countries compete in diplomatic campaigns. This study, through multiple survey experiments, uncovers the effect of being silent, issuing positive justification, and negative accusation, in interaction with the opponent's strategy. We demonstrate that negative verbal attacks work and undermine the target's popularity as they do in electoral campaigns. Unlike domestic electoral campaigns, however, negative diplomacy has little backlash and persuades people to support the attacker. Consequently, mutual verbal fights make neither party more popular than the other. Nevertheless, this does not discourage disputants from waging verbal fights due to the structure similar to the one-shot prisoner's dilemma. We also find that positive messages are highly context-dependentthat is, their effects greatly depend on the opponent's strategy and value proximity between the messenger and the receiver.

Many scholars argue that economic interdependence and more extensive economic ties between countries decreases the risk of violent conflict between them. However, despite considerable research on the capitalist peace at the macro or dyadic level, there has been less attention to its possible individual-level microfoundations or underpinnings. We argue that public perceptions about economic ties with other states and the costs of conflict should influence the expected constraints on the use of force for leaders. Actual high interdependence and potential economic costs may not suffice to create political constraints on the use of force if people are unaware of the degree of interdependence or fail to understand the benefits of trade and the likely economic costs of disruptive conflict. We examine the linkages between individual perceptions about economic interdependence and their views on conflict and peace through a survey experiment, where we ask respondents in Japan about approval for belligerent actions in a territorial dispute with China and varying information about economic ties. Our findings indicate that greater knowledge and information about economic interdependence affects attitudes about territorial disputes and increases support for peaceful solutions with China.

Which factors drive the onset of genocidal violence? While the previous literature identified several important influences, states' military capabilities for conducting mass-killings and the structure of their security forces have received surprisingly little attention so far. The authors take this shortcoming as a motivation for their research. A theoretical framework is developed, which argues that more differentiated security forces, that is, forces that are composed of a higher number of independent paramilitary and military organizations, are likely to act as a restraint factor in the process leading to state-sponsored mass-killings. Quantitative analyses support the argument for a sample of state-failure years for 1971-2003, and it is also shown that considering a state's security force structure improves our ability to forecast genocides.

Several studies have claimed that changes in the political leadership of a country affect foreign policy decision making. The following paper systematically tests this in the context of states' participation in military coalition operations. By building on previous theoretical models, the authors argue that new leaders may differ from their predecessors in that the former (i) have dissimilar preferences with regard to the involvement in military interventions, (ii) evaluate relevant information differently, and (iii) are less likely to be entrapped in intervention policies. Ultimately, the net effect of these factors should make it more likely that political leadership turnovers are associated with premature withdrawals from ongoing military coalitions. The theory is tested by quantitative analyses of newly collected data on military coalition operations in 1946-2001 and a qualitative case study. The authors find strong and robust support for their argument.

Existing research emphasizes how United Nations Security Council (UNSC) approval helps convey information to domestic audiences that military action is conducted with good intentions, for desirable consequences and in a legitimate manner. This information transmission mechanism can also increase support for UNSC-endorsed military action in countries unlikely to provide major contributions to military actions. There is some cross-national evidence supporting the information transmission mechanism in the United States. Examining the causal mechanisms underlying foreign public support for US military action through a survey experiment with approximately 2,000 respondents in Japan shows that foreign public support varies depending on whether the military action has UNSC approval. The process of presenting draft resolutions to the UNSC also affects public support.

When it comes to buying military aircraft, what leads states to prefer one supplier over the other? This paper explores this question from the perspective of international relations theory. First we use social network analysis to map out fighter jet transfers during and after the Cold War and examine the extent to which historical structures of international hierarchy shape contemporary supplier-receiver relationships. Next, we use a basic probit model to analyse the origins of fighter jets in the world's air forces today to evaluate the effect of interstate orders of super-ordination and sub-ordination on sourcing patterns. All things being equal, the more a state is embedded in US security and economic hierarchy, the more it is likely to buy American-made fighter jets.

The United States uses two forms of multilateralism to increase levels of foreign public support for military action: diplomatic multilateralism and operational multilateralism. Diplomatic multilateralism is typically done by obtaining a United Nations Security Council resolution authorizing military action. The use of multinational forces, the so-called coalition of the willing and many flags program, is an example of operational multilateralism. While scholars have empirical evidence that diplomatic multilateralism generates foreign domestic support for the use of force, there is no equivalent study for operational multilateralism. We do not know if or how much the two types of multilateralism would differ in inducing foreign domestic support for military action. This article, by using Japan as a field of survey experiment, answers these questions.

The use of force is prohibited under the UN Charter. An exception is written in Article 51, which allows a state to conduct an act of self-defense. This study explains why only some states invoke it. The author claims that the baseline probability of claiming the right remains low because explicit reference to Article 51 accompanies the uncertainty of justification success and poses legal and diplomatic costs. However, balanced escalation and no alliance relationship negate those costs and increase the likelihood of self-defense justification. Moreover, under the strict conditionality, minor powers receiving American military aid frequently and promptly claim self-defense.

The export of arms belongs to the most contested issues in democracies. In this article, we examine the economic repercussions of the recent easing of the Japanese arms exports restrictions. We develop a rational expectations argument to understand why some political events increase the income of the arms manufacturers, while other ones reduce it or have no effect at all. Event studies suggest that investors closely observe relevant political developments since stock prices of the six arms manufacturers companies reacted consistently to the announcements and leaks as to whether the arms export restrictions would be lifted or not.

This article aims to demonstrate that differences in the two major datasets can significantly affect the results of predictions of mass political killing. Mass political killing (such as Hitler's killing of some six million Jews, or the Rwanda genocide of 1994) has been studied for decades with the aid of valuable datasets measuring 'democide' and 'genocide and politicide', respectively. Without attempting to take sides as to whether one or the other is a more valid measure of the phenomenon of mass political killing, the authors aim in this investigation to see what independent variables best account for the onset of mass political killing, with the state-year as the unit of analysis. The predictor variables are level of economic development; types of war and violent unrest short of war; and regime type. By using a Cox proportional hazard model, the authors find that important regime effects either appear or disappear depending on the dataset used, with regime generally having a significant effect on onset of democide, but not having a significant effect on onset of geno-politicide. It is important for the scholarly community to be aware of these dataset effects, which may be the source of some of the most important existing controversies in the literature on explaining mass political killing.

This article aims to demonstrate that differences in the two major datasets can significantly affect the results of predictions of mass political killing. Mass political killing (such as Hitler's killing of some six million Jews, or the Rwanda genocide of 1994) has been studied for decades with the aid of valuable datasets measuring 'democide' and 'genocide and politicide', respectively. Without attempting to take sides as to whether one or the other is a more valid measure of the phenomenon of mass political killing, the authors aim in this investigation to see what independent variables best account for the onset of mass political killing, with the state-year as the unit of analysis. The predictor variables are level of economic development; types of war and violent unrest short of war; and regime type. By using a Cox proportional hazard model, the authors find that important regime effects either appear or disappear depending on the dataset used, with regime generally having a significant effect on onset of democide, but not having a significant effect on onset of geno-politicide. It is important for the scholarly community to be aware of these dataset effects, which may be the source of some of the most important existing controversies in the literature on explaining mass political killing.

Why do some democracies break their security commitments whereas others do not? This study proposes a research strategy to answer the question by analyzing the timing of unilateral exits from a coalition military operation. Coalition participants typically do not exit until a military mission has been accomplished. However, in the case of the US-led coalition occupying Iraq since May 2003, 16 states have unilaterally withdrawn their armed forces. Despite the danger such defections may cause to the relationship of these states with the USA, why and when do they exit? The author creates a dataset with a state-month unit of analysis that contains information on 37 partner states and applies a Cox proportional hazard model. The study finds that the occurrence of a national election serves as a strong driving force to accelerate an exit from the coalition. An incumbent leader who faces a challenger who opposes military contributions in Iraq would reverse the policy to support the USA and exit the coalition to win an election, even at the risk of damaging a bilateral relationship with the USA. A change in leadership after an election, on the other hand, failed to be a predictor of the timing of defection. Furthermore, results reveal that the division of power within the government and the constitutional rules that enable significant parliamentary control over executive decisions to use force neither delay nor accelerate the timing of withdrawal. To understand the conditions under which democracies break their security commitments, more attention should be paid to election cycles than to a change in leadership and to types of democratic institutional and constitutional arrangements.

Why do some democracies break their security commitments whereas others do not? This study proposes a research strategy to answer the question by analyzing the timing of unilateral exits from a coalition military operation. Coalition participants typically do not exit until a military mission has been accomplished. However, in the case of the US-led coalition occupying Iraq since May 2003, 16 states have unilaterally withdrawn their armed forces. Despite the danger such defections may cause to the relationship of these states with the USA, why and when do they exit? The author creates a dataset with a state-month unit of analysis that contains information on 37 partner states and applies a Cox proportional hazard model. The study finds that the occurrence of a national election serves as a strong driving force to accelerate an exit from the coalition. An incumbent leader who faces a challenger who opposes military contributions in Iraq would reverse the policy to support the USA and exit the coalition to win an election, even at the risk of damaging a bilateral relationship with the USA. A change in leadership after an election, on the other hand, failed to be a predictor of the timing of defection. Furthermore, results reveal that the division of power within the government and the constitutional rules that enable significant parliamentary control over executive decisions to use force neither delay nor accelerate the timing of withdrawal. To understand the conditions under which democracies break their security commitments, more attention should be paid to election cycles than to a change in leadership and to types of democratic institutional and constitutional arrangements.

There is an empirical evidence of an aid-for-policy deal between the United States and other states; the United States has utilized aid programs to promote affirmative votes in the UN General Assembly and to maintain an alliance relationship with strategically important states. However, whether there is a systematic evidence of an aid-for-participation deal remains inconclusive. Does the United States generally utilize its foreign aid to reward the contribution of troops to the US-led multinational forces and to punish the lack of contribution? The author argues that US foreign aid is used to prevent free-riding in coalition participation. To test the argument, I examined whether states were punished or rewarded by the United States for their behavior in sending or failing to send troops to 15 post-Second World War US-led coalition forces. The results show that the United States punished states for unexpected nonparticipation, but did not always provide rewards for support.

There is an empirical evidence of an aid-for-policy deal between the United States and other states
the United States has utilized aid programs to promote affirmative votes in the UN General Assembly and to maintain an alliance relationship with strategically important states. However, whether there is a systematic evidence of an aid-for-participation deal remains inconclusive. Does the United States generally utilize its foreign aid to reward the contribution of troops to the US-led multinational forces and to punish the lack of contribution? The author argues that US foreign aid is used to prevent free-riding in coalition participation. To test the argument, I examined whether states were punished or rewarded by the United States for their behavior in sending or failing to send troops to 15 post-Second World War US-led coalition forces. The results show that the United States punished states for unexpected nonparticipation, but did not always provide rewards for support. © The author [2008]. Published by Oxford University Press in association with the Japan Association of International Relations
all rights reserved.

Why do states join US-led military coalitions? The war/dispute-diffusion literature suggests that opportunity and willingness are crucial determinants of coalition participation (Siverson snd Starr.1990, 1991). A state joins a coalition if it has a strong interest in war and enough capability to send armed forces abroad. Alliance studies connect coalition participation problems with the reliability of allied countries (Leeds, 2003 Gartzke and Gleditsch, 2004). These studies seem to provide a fairly good picture on the question
however, they are not free of problems. In particular, they study only coalitions for interstate war and militarized disputes but ignore coalitions for other purposes. Coalitions can be formed for military operations other than war (Kober, 2002). There are coalitions for humanitarian intervention, peacekeeping, and even for the evacuation of noncombatants. This article shows how difference in operation-types and collective legitimacy affect the decision of a state to participate in US-led coalitions. A coalition with United Nations' authorization may appear to be a legitimate international 'police' act and attract more partner states. A coalition for intervention into domestic affairs may be less attractive to possible participants because of the violation of the noninterference norm of international law. Statistical analysis on United States coalition partners from 1950 to 1999 suggests that how and for what purposes coalitions are formed cannot be overlooked. Coalition participation is not fully explained by the existing perspectives found in war/dispute-diffusion literature and alliance studies, and there is a need to invok 'the compulsion of the coalition's missions and legitimacy'. © The author [2007]. Published by Oxford University Press in association with the Japan Association of International Relations
all rights reserved.

Why do states join US-led military coalitions? The war/dispute-diffusion literature suggests that opportunity and willingness are crucial determinants of coalition participation (Siverson and Starr, 1990, 1991). A state joins a coalition if it has a strong interest in war and enough capability to send armed forces abroad. Alliance studies connect coalition participation problems with the reliability of allied countries (Leeds, 2003; Gartzke and Gleditsch, 2004). These studies seem to provide a fairly good picture on the question; however, they are not free of problems. in particular, they study only coalitions for interstate war and militarized disputes but ignore coalitions for other purposes. Coalitions can be formed for military operations other than war (Kober, 2002). There are coalitions for humanitarian intervention, peacekeeping, and even for the evacuation of noncombatants. This article shows how difference in operation-types and collective legitimacy affect the decision of a state to participate in US-led coalitions. A coalition with United Nations' authorization may appear to be a legitimate international 'police' act and attract more partner states. A coalition for intervention into domestic affairs may be less attractive to possible participants because of the violation of the noninterference norm of international law. Statistical analysis on United States coalition partners from 1950 to 1999 suggests that how and for what purposes coalitions are formed cannot be overlooked. Coalition participation is not fully explained by the existing perspectives found in war/dispute-diffusion literature and alliance studies, and there is a need to invoke 'the compulsion of the coalition's missions and legitimacy'.

US presidents used military force 212 times from 1948 to 1998. In 45 of these cases, the force was embedded in a multilateral context. The article distinguishes between procedural multilateralism, where US military operations are endorsed by an international organization, and operational multilateralism, where military actions are coordinated with the armed forces of other countries. In some cases, such as the Korean War and the first Gulf War, the United States obtained UN authorization and created a multinational force. However, there are also partially multilateral cases, in which either political endorsement or execution of the use of force is made by a multilateral approach while the other is subject to unilateralism. This article focuses on the varieties of multilateralism and homes in on exploring why such varieties of multilateralism exist. An original dataset for studying multilateral-unilateral choice in US use of force is analyzed using a multinomial logit model and a bivariate probit model. The analyses suggest that three domestic conditions - recession, election cycle, and divided government - can cause partial multilateralism, since they create different incentives for the president to seek burden-sharing with allies or seek collective legitimacy in international organizations. © 2005 Journal of Peace Research.

US presidents used military force 212 times from 1948 to 1998. In 45 of these cases, the force was embedded in a multilateral context. The article distinguishes between procedural multilateralism, where US military operations are endorsed by an international organization, and operational multilateral ism, where military actions are coordinated with the armed forces of other countries. In some cases, such as the Korean War and the first Gulf War, the United States obtained UN authorization and created a multinational force. However, there are also partially multilateral cases, in which either political endorsement or execution of the use of force is made by a multilateral approach while the other is subject to unilateralism. This article focuses on the varieties of multilateralism and homes in on exploring why such varieties of multilateralism exist. An original dataset for studying multilateral-unilateral choice in US use of force is analyzed using a multinomial logit model and a bivariate probit model. The analyses suggest that three domestic conditions - recession, election cycle, and divided government - can cause partial multilateralism, since they create different incentives for the president to seek burden-sharing with allies or seek collective legitimacy in international organizations.

国際政治学における計量分析の活用は我が国ではまだ限定的であるが,海外では非常に盛んである.学術誌を見ても計量手法の存在感は圧倒的である.この背景には,合理的選択論を軸とする戦争原因研究の理論的進展とそれに影響された他分野の理論研究に計量手法が大きな役割を果たしてきたことがある.ここでは国家間武力紛争,武力行使,同盟と有志連合という三つのトピックについて最近の研究を紹介し,それを通じて代表的なデータセット,分析単位,手法を明らかにしていく.

The monumental works by Inis Claude Jr. have led many scholars of International Relations to regard collective legitimization as one of the most important mechanism for the institutionalization of international relations. This paper explores the enhancement of international institutions by focusing on the US collective legitimization in the Dominican intervention (1965) and the Cuban Missile Crisis (1962).<br>This paper argues that collective legitimization enhances institutionalization of international relations in two different ways: constraining the US decision about its military actions, and expanding the roles and functions of the formal international organizations. In the case of the Dominican intervention in 1965, due to opposition by other countries in the region, the US failed to continue deployment of its troops, especially the Army and Air Force, as it wished. The US also reluctantly accepted a Brazilian general for the commander of the Inter-American Peace Forces even though it wanted an American commander. In addition to these constraints, as a result of creation of Inter-American Peace Forces, the roles and functions of the OAS were expanded into peace-keeping operations and humanitarian military operations, neither of which was within the scope of the Charter of the OAS.<br>A comparison of the Dominican Intervention in 1965 with the Cuban Missile Crisis shows there are two strategies of collective legitimization: assertive (offensive) legitimization and negative (defensive) legitimization. Assertive legitimization is a strategy whereby the United States tries to show the legality and justice of its military actions by gaining formal support from international institutions. Negative legitimization is a strategy whereby the United States tries to show the legality and justice of its military actions by denying the claim of an enemy or counterpart such as Cuba or the USSR. In the Dominican Intervention, the United States utilized assertive legitimization. The OAS, which legitimized the US position, was institutionalized considerably; but the UN, which was bypassed by the US, was not institutionalized. In the Cuban Missile Crisis, on the other hand, the United States chose negative legitimization. Neither the UN, nor the OAS was institutionalized. From these empirical analyses, this paper provides a new hypothesis that assertive legitimization by the United States enhances institutionalization of international relations more than negative legitimization.

In international crisis, the United States uses its military power under two approaches: the multilateral and the unilateral approach. The multilateral approach was used in the Persian Gulf War, while the unilateral approach was used in the 1989 u.s. intervention in Panama. How many military interventions were exercised as multilateral actions? How often the United States utilized its military power unilaterally? This paper would answer to the question. As is widely known, there have been many datasets on military actions and wars, such as COW, 1GB, MID, and KOSIMO; however none of them pro...

見えない危機の現象が今までよりも頻繁に起こっていることを踏まえ（例、インド・パキスタン、中国・台湾、日本・韓国）、それらの事例の精査を行うほか、関係した実験の計画を実施した。2018年12月に起こった日本と韓国の間におけるレーダー照射事件は本研究のターゲットにしている見えない危機として示唆に富む事案であり、それをモチーフにした実験を計画し、そのデータ処理を進めた。2017年に本研究チームで公刊したPolitical Communication誌掲載の実験をリーダーの名前を伴って拡張する実験については国際会議での発表を行った上でその追加の実験を2回実施した。リーダーがどのように情報を伝えることがその言葉の信ぴょう性を高め、見えない危機をめぐる国民の態度決定に影響するのかを見極めることが重要な課題であったが、現時点での暫定的な分析結果では良好な知見が得られた。2019年6月にはオスロの国際平和研究所（Peace Research Institute, Oslo）やスウェーデンのウプサラ大学、台湾の中央政治院などでの口頭発表を実施したほか、11月には香港大学において小濵・多湖の両名が報告を行い、数々のコメントを得て、論文を完成させ、国際学術雑誌に投稿している。また、2019年度末には危機に際してエリートとそうでない者が違うリアクションをするのかについてオリジナルな実験デザインを着想し、サーベイ実験として実施した。この結果は国際会議での報告を2020年度に予定する。

2019年度は2018年度に取得した韓国レーダー照射事件についてのパネルデータ、および複数のメディア（マスメディア・インターネット・対人的コミュニケーション）の第三者効果についてのWeb調査データの分析結果について、日本心理学会、日本社会心理学会において研究発表を行った。さらには、大学院生や研究員との共同研究による結果が、国内外の査読付き論文誌において掲載された。
加えて、これまでの年度において得られた調査データの整理を行うととともに、複数のマスメディア・ウェブメディアの議題設定効果を測定するためのパネルデータの1波データを日経リサーチ社の協力を得て測定した。データ取得は3月であり、新型コロナウイルス感染症の拡大がみられた時期であったことから、他の争点についての報道量は少なくなっていた。しかし、このような時期において争点重要性がどのような影響を受けるのか、あるいは、グローバルに拡大する感染症というある意味での外的危機に際して、議題設定や旗下集結効果が生じるのか否かを検討できるデータが取得できたことの意義は大きい。
また、同時にソーシャルメディア上での発信についても分析できるユーザーローカル社のSocial insightというツールの契約を行うことができたため、2020年夏の第2波調査に向けてWeb上の情報発信について検証を行うことのできる環境が整った。それに加えて、メディアの効果を検証するためのクラウドソーシングサービスを利用したWeb調査実験を複数実施することができた。

日韓関係における紛争、特に歴史問題と領土問題に焦点を絞り、両国における世論とメディアの関係について社会心理学、政治学、情報学を含む学際的アプローチで研究を行った。社会心理学および政治学的アプローチを用いた一連のオンライン実験からは、パブリックディプロマシー動画の視聴によって日韓協力の必要性の認識が高まること、日本と韓国の経済力の差が縮まりつつあるという認識が歴史問題や領土問題に関する日本の世論を硬化させることなどを明らかにした。一方、新聞記事データの分析からは日本と韓国で歴史問題や領土問題が異なるフレームで報道されていることが明らかにされた。これらの成果は英文査読誌や国際会議で発表された。

日本の国際関係研究においては理論・歴史間の対話が欠けており、相互刺激に基づく研究上の新たな展開は稀薄である。本研究では、過去および海外の対話状況を検討し、今日可能な理論・歴史対話の条件や方法を考察した。
国際関係のマクロ理論の論争や合理的選択論の普及を背景に、理論・歴史対話は困難になっている。しかし日本やアメリカなどでは、理論を換骨奪胎しながらも利用し、歴史研究の対象や観念を転換した例がある。今日、理論的パラダイムを歴史研究に応用し、歴史から抽出したパターン自体を理論化するのは難しい。しかし理論上の基本的概念は、歴史的に吟味すべき課題を抱えており、また歴史的現象を再解釈する手がかりになる。

本研究の代表者および分担者は、主要な成果として英語論文、合計11部を作成し、平成29年3月に、シュプリンガー社からGames of Conflict and Cooperation in Asiaという題目の編著書籍を公刊した。本編著書では、グローバル・ガバナンスを基調に分析枠組みを構築し、アジアにおいてはその多様性から域内のみで政策協調を確保することは難しいため、域外の国々やグローバル制度と連携することが協調の実践的工夫となっている。この点を勘案して本編著書では、地域ガバナンスとグローバル・ガバナンスとの制度的連携について、安全保障、貿易、通貨・金融という政策領域において分析した。

多数の国家および問題領域にわたる分析から、異質な主体が混在するシステムで相互依存が深まると、その衝突が原因となる新たなリスクが存在することを具体的に明らかにした。そして、これらの事例分析の成果に、数量分析およびシミュレーション分析を有機的に結合させることで、現在の国際システムにおけるパワーシフトが、異質性と共存することによって生み出される新たなリスクについて理論化を行った。

本プロジェクトは、法と政治の両面をミックスさせながら、武力行使をめぐる諸論点を扱い、それを英語で国際水準の知的生産物として発表していくことが目的であった。武力行使を始めるにあたって自衛権を発動するか否かの論点には、アメリカの援助コンディショナリティが重要な役割を果たしていることを実証的に示した。また、多角的に国連安保理からの授権決議を得てから武力行使をする場合については、第三国の民意を得られるからという理論的な見解に沿いつつ、それが妥当しない条件をサーベイ実験の手法で確認した。すでに4本以上のSSCIジャーナル掲載の英語論文があり、今後も同様の媒体に発表をする予定である。

日本と韓国の間の領土問題に関連する国内・国外の研究は豊富である。本格的な研究書を取り上げても、たとえば、玄大松の『領土ナショナリズムの誕生』などが存在する。しかし、領土問題をめぐる民意に関して仮想的なシナリオを被験者に提示しその反応を観察するという、サーベイ実験手法を用いた研究は、国内外問わず乏しい。また、世論が領土問題に対する政府の対応の違いをどのように認識し、かつ、その違いが仮想の国政選挙での投票行動に与える影響は、従来の研究で十分に分析されておらず、本研究はその課題を解決することを狙いとした。サーベイ実験の結果、従来有効とされてきた国際司法裁判所の判決効果が乏しいことがわかった。

日本の国際関係理論は海外の諸理論の輸入に依存し、独自性に乏しいとされる。本研究は、過去の主要な理論に関して、その輸入の態様を洗い直し、そこに「執拗低音」（丸山真男）のようにみられる独自の問題関心や分析上の傾向を検出した。
日本では、先行する歴史・地域研究を背景に、理論研究に必然的に伴う単純化や体系化よりも、現象の両義性・複合性を捉えようとする傾向が強く、また新たな現象と分析方法の中に、平和的変更の手がかりを摸索する場合が顕著にみられた。海外の理論を刺激として、従来からの理念や運動、政策決定に関する関心が、新たな次元と方法を備えたケースも多い。

本研究は、貿易、通貨、平和維持、温暖化防止等のグローバル問題を扱う国際ガバナンスにおける提携形成と制度設計という課題の実相を分析し、改善策を探求した。国々の提携を大規模にすれば、グローバル問題の解決を図る上で好都合だが、多種多様の国家の参加を募ることによって緩やかな行動規範しか採択できない。反対に、小さな提携はその相似性から強力な規範を採択できるが、問題解決には規模の面で不十分となる。本研究は、権力や認識を重視する政治学の手法、主体の合理的行動や制度の合理的基盤を精査する経済学の手法を適用することによって、両課題を包括的に分析し、課題間に内在するジレンマを縮小する方途を解明した。

アメリカが主導する多国籍軍について包括的なデータセットを整備し、それを計量手法と事例比較手法を用いて科学的に分析した。日本らしい国際関係論の研究として、国際政治における力の要素だけではなく、国際法や外交規範の重要性を意識した議論を心がけ、複数の英語論文を執筆・公表した。また、チューリヒ大学とNATOに所属する共同研究者とともに有志連合に関する最新研究を開始し、研究代表者の単著論文と合わせて、多国籍軍・有志連合をめぐる国内政治と国際政治に関する因果メカニズムの解明も行った。

本研究は、国際関係学と経済学の専門家を糾合しながら、安全保障と政治経済の領域における紛争と対立の背景にある共通問題を解明し、それらの問題を解明する分析法を構築しながら、同問題を解決する制度を探究しようとするものである。本研究が着眼した問題とは、(1)主体間で適切な協調関係を形成することに関わる提携形成および調整の問題、(2)有限価値を主体間で円満に分配するという分配問題、(3)分配や主体の行動に関して、信頼可能な約束を樹立するという約束履行問題であり、これらの問題を分析するのに適したモデルを構築し、モデルを基に解析作業を行った。その結果、紛争の特性を包括的に解明し、紛争を協調に転換する諸制度を析出した。

3年目の本年は、国際政治における正当化・正当性をめぐって研究の総仕上げを行うこと、また、今まで作成してきたデータセットを分析し終え、それを適宜まとめて発表することに力を注いだ。具体的には、二つの研究課題を設定した。第一に、アメリカが武力行使をするにあたって、正当性を議会の承認という形で「国内調達」する場合と国際法に準拠して国際機構からの授権を得ることで「国外調達」する場合がなぜ異なるのかを問う研究をまとめた。第二に、2003年5月以降のイラク占領に伴う有志連合から離脱する国の属性と条件について分析を行い、正当性を欠く軍事作戦においてどのような場合に連合参加国が大義名分を失い部隊撤退を決めるのかを論じた。
第一の分析では、アメリカ議会が大統領の所属政党と同じ政党によってコントロールされている場合(いわゆる「統一政府」)においては武力行使をめぐる正当性の国内調達が追求されやすく、他方、議会多数派と大統領の所属政党が違う、いわゆる「分割政府」においては正当性の外部調達が追求されやすいとわかった。この研究成果は博士論文として東京大学大学院総合文化研究科に提出され、2007年2月28日に学位論文として合格した。なお、これ以後はこれを早期に出版することが課題である。
第二の分析については、有志連合から離脱する国にとって選挙日程の影響が小さくないことがわかった。すなわち、選挙が実施されるたびに連合離脱の誘因が高まる。ただし、それは選挙に伴うリーダーシップの交代に因るのではなく、選挙において現職候補が人気のない政策を自ら転換する強いインセンティブを持つためであると考えられる。この研究成果は2007年4月に開催されるMidwest Political Science Association年次大会、2007年9月に開催されるAmerican Political Science Association年次大会で発表予定である。また、ある英語ジャーナルにおいてRevise and Resubmitの状態にある。

三年目の本年は、研究成果をまとめることに力を注いだ。(1)国際組織を活用することが米国の軍事行動を長期化させることを発見したという論文、(2)米国の国際組織活用の傾向が経済情勢と分割政府(divided government)によって左右されるという議論を展開する論文を作成した。当初から予定していたように、英語で論文を執筆し、現在、投稿中である。本については既に年度の初めにJournal of Politicsに対して投稿を行ったが、三人のレフェリーのうち、一人が即掲載可、一人が条件付で掲載可、一人が掲載不可の裁定を下し、最終的には不採用になった。問題は理論部分が弱いこととされ、その点について継続的に修正を施した。また、二本目の論文を執筆した。
年度の後半は二つの論文について校正を繰り返した。現在、Journal of Peace ResearchおよびJournal of Conflict Resolutionに対して投稿を行っている。本年度中に成果を掲載できなかったことは残念であるが、早期に上記で挙げたような北米の学術雑誌に掲載される論文を仕上げたいと考えている。なお、このプロジェクトで作成したデータセットは論文を学術雑誌上に発表した段階でホームページを通じて公表する方針である。また、2004年4月にシカゴで開かれるMid-west Political Science Associationの年次大会で成果報告を行う予定である(Duration of the US Use of Force and Institutional Effects of Multilateral Military Actions)。