The words you need to know

The basic unit of international relations. A state has a defined territory, a permanent population, a government, and the capacity to enter into relations with other states. The last condition matters: a state is recognised by other states. Without recognition, territory and a government are not enough. The question of when a state is a state is one of international relations' most persistent practical problems.

The supreme authority of a state over its own territory and population, and its freedom from external interference. The foundation of the modern international system since the Peace of Westphalia in 1648. Sovereignty means no state has the right to interfere in another's internal affairs. In practice, great powers interfere constantly. The tension between the principle of sovereignty and the practice of intervention is one of international relations' central contradictions.

In international relations, the absence of a central authority above states. Not chaos: anarchy here means there is no world government, no police force for nations, no court that can compel compliance. States operate in an anarchic system where they must ultimately rely on themselves. This single condition drives much of IR theory: how do states behave, and how do they cooperate, when there is no one to enforce the rules?

The goals and ambitions of a state in the international arena: security, economic prosperity, territorial integrity, influence. Foreign policy is, in theory, the pursuit of the national interest. In practice, national interest is defined by whoever holds power, and different governments define it differently. "Acting in the national interest" is both a description and a justification. The two are often confused.

Entities that exercise significant influence in international relations without being states. Multinational corporations, international organisations, NGOs, terrorist organisations, religious movements. The classical view of IR focused entirely on states. Non-state actors complicate this: a company like Apple has a GDP larger than most countries. A terrorist network can destabilise a region. The international system is increasingly shaped by actors who are not states.

The oldest and most influential theory of international relations. States are the primary actors, the international system is anarchic, and states pursue power and security above all else. International cooperation is possible but fragile: states cooperate when it serves their interests and defect when it doesn't. Morality and idealism are luxuries states cannot afford. Thucydides, Machiavelli, and Hans Morgenthau are the canonical realists. Most practitioners of foreign policy operate on broadly realist assumptions even when they don't use the word.

The theory that states can cooperate sustainably through institutions, trade, and shared norms. Democracies tend not to fight each other (the democratic peace). Economic interdependence raises the cost of conflict. International institutions like the UN and WTO create frameworks for cooperation. Where realism sees anarchy as permanent and dangerous, liberalism sees it as manageable through the right structures. Dominant in Western foreign policy thinking from 1945 to the 2010s. Under sustained pressure since.

The theory that the most important structures in international relations are social rather than material: shared ideas, norms, identities, and beliefs. States' interests are not fixed by nature; they are constructed by how states see themselves and each other. The end of the Cold War, which realism failed to predict, strengthened constructivism's claim: the Soviet Union did not collapse because of material weakness alone, but because of shifts in identity and belief inside the system.

Kenneth Waltz's revision of classical realism, focusing on the structure of the international system rather than human nature. States balance power because the anarchic structure compels them to, not because they are inherently aggressive. The distribution of power across the system determines behaviour. Offensive realism (Mearsheimer) adds that states always seek to maximise relative power. Defensive realism argues states seek only sufficient security. The debate between them is one of IR's most productive.

The use of military force or economic coercion to influence other states. Threatening, sanctioning, invading. The most direct form of power: do what we want or face consequences. Effective in the short term, often counterproductive over time. Hard power shapes behaviour through compulsion rather than persuasion.

The ability to attract and persuade rather than compel. A country's culture, values, and foreign policy credibility can make others want to align with it. Joseph Nye coined the term in 1990. American soft power at its peak: Hollywood, universities, the appeal of democracy and freedom. Soft power works slowly and is difficult to measure. It is also fragile: consistent behaviour that contradicts stated values erodes it quickly.

The dominance of one state over others in the international system, providing the stability and rules that others operate within. A hegemon sets the terms: the currency of trade, the rules of institutions, the norms of behaviour. The US has been the dominant hegemon since 1945. Hegemonic stability theory holds that the world is more orderly under hegemony. The question now being tested: what happens when hegemony declines?

The distribution of power among states such that no single state can dominate the others. States balance against rising powers through alliances or internal military development. The European system before World War One was an attempt at balance of power. It failed. Balance of power theory is descriptive (states do balance) and prescriptive (they should). The two are regularly confused.

The number of major power centres in the international system. Unipolar: one dominant power (the US after 1991). Bipolar: two (US and USSR during the Cold War). Multipolar: several roughly equal great powers (pre-1914 Europe). Theorists disagree on which is most stable. Bipolarity has defenders: two superpowers who know each other's capabilities may be more predictable than multiple competing powers whose intentions are less clear.

An international system with multiple significant power centres: the US, China, Russia, the EU, India, and others each exercising meaningful independent influence. The post-Cold War unipolar moment is widely considered to be ending. What replaces it is the defining question of current international relations. Multipolarity is not inherently stable or unstable; it depends on whether the powers have compatible or conflicting interests and whether institutions can manage the competition.

The rivalry between the world's most powerful states for influence, resources, and strategic advantage. The term entered mainstream use in US strategic documents around 2017–2018 to describe the growing contest with China and Russia. It signals a shift from a focus on terrorism and rogue states to a focus on peer adversaries capable of challenging US dominance across multiple domains: military, economic, technological, diplomatic.

Preventing an adversary from taking an action by convincing them the costs will outweigh the benefits. Nuclear deterrence is its most extreme form: the threat of mutual destruction prevents nuclear use. Conventional deterrence works through credible military capability and political will. Deterrence requires three things: capability (you can do what you threaten), credibility (the adversary believes you will), and communication (they understand the threat). Remove any one and deterrence fails.

The condition in which two nuclear-armed states each have the ability to survive a first strike and retaliate with devastating effect. If attacking guarantees your own destruction, you don't attack. MAD is the logical foundation of nuclear deterrence between the US and USSR/Russia. It is called a doctrine but it is better understood as a condition: it exists whether or not anyone chooses it. The stability it provides is real. The stability it requires is terrifying.

The paradox in which one state's attempt to increase its own security makes other states feel less secure, prompting them to arm in response, which makes the first state less secure. Arms races emerge not from aggression but from fear. The security dilemma is a structural problem of the anarchic international system: in the absence of trust, defensive measures look offensive. Many wars have been started not by aggressors but by states reacting to perceived threats from states that were themselves reacting to perceived threats.

A conflict in which two major powers support opposing sides without fighting each other directly. The Cold War produced many proxy wars: Korea, Vietnam, Angola, Afghanistan. The major powers supply weapons, money, training, and intelligence, and avoid direct confrontation. Proxy wars allow great powers to contest each other's influence while managing the risk of direct conflict, particularly nuclear escalation.

A strategy combining conventional military force with irregular tactics, cyberattacks, disinformation, economic coercion, and political subversion. Designed to achieve strategic objectives below the threshold of declared war, making attribution difficult and response complicated. Russia's actions in Ukraine from 2014 onward, China's activities in the South China Sea, and interference in elections are cited as examples. The term is contested but has become standard in defence policy.

Conflict between opponents with significantly different military capabilities, where the weaker party compensates through unconventional tactics. A state with advanced military technology versus a non-state actor using guerrilla tactics, IEDs, and civilian infrastructure. The US in Afghanistan is the canonical modern example: overwhelming conventional superiority that could not translate into strategic success against an adversary fighting a different kind of war.

A state that has lost the ability to perform the basic functions of government: maintaining order, providing services, exercising a monopoly on the use of force within its territory. Somalia, Libya post-2011, and parts of Yemen are regularly cited examples. Failed states create security vacuums that other states, non-state actors, and criminal organisations fill. They are both a humanitarian problem and a security problem for neighbouring states and the international system.

The management of relations between states through negotiation, communication, and representation rather than force. Ambassadors, treaties, summits, back channels: all diplomacy. The alternative to diplomacy is not necessarily war, but the absence of managed communication makes conflict more likely. States maintain diplomatic relations even with adversaries because the channel itself has value independent of the relationship's warmth.

Economic or political penalties imposed on a state or individual to compel a change in behaviour, without resorting to military force. Trade restrictions, asset freezes, travel bans. Sanctions signal displeasure and impose costs. Their effectiveness is debated: they rarely change the behaviour of authoritarian regimes determined to resist them. They are nonetheless a standard tool of foreign policy, partly because they are visible and politically satisfying even when they don't work.

The strategy of preventing an adversary from expanding its power and influence beyond its current boundaries, without directly attacking it. George Kennan articulated containment as US strategy against the Soviet Union in 1946. Rather than rollback (actively pushing the USSR back), containment aimed to hold the line and wait for internal contradictions to weaken the adversary. It became the dominant framework of US Cold War strategy. The concept is now applied to China.

Making concessions to an aggressive power in the hope of preventing conflict. Now almost universally pejorative, because of the 1938 Munich Agreement in which Britain and France allowed Hitler to annex the Sudetenland in exchange for promises of no further expansion. The promises were broken. "Appeasement" is now invoked to argue against any concession to an adversary. The historical lesson is applied broadly and sometimes carelessly: not all concessions are appeasement, and not all adversaries are Hitler.

An area or group of states over which a great power exercises dominant or exclusive influence. The Monroe Doctrine (1823) declared the Western Hemisphere a US sphere of influence. The Soviet Union maintained a sphere of influence in Eastern Europe. Spheres of influence are not formal legal arrangements but they are real constraints on the autonomy of states within them. The assertion of a sphere of influence by one great power is typically resisted by others.

Conducting international relations through multiple states or international organisations rather than through bilateral deals. The UN, NATO, the WTO, the Paris Agreement: all multilateral frameworks. Multilateralism assumes shared interests and shared norms. When those break down, multilateral institutions become arenas for competition rather than cooperation. The tension between multilateral commitments and national interest is permanent.

Joining the dominant or rising power rather than balancing against it. The opposite of balance-of-power behaviour. Weaker states sometimes calculate that aligning with the powerful is safer than opposing them. Small states in the shadow of great powers often face this choice. Whether states balance or bandwagon depends on the nature of the threat, the availability of allies, and what the dominant power is offering.

The norm established by the UN in 2005 that sovereignty is not absolute: if a state fails to protect its population from genocide, war crimes, crimes against humanity, or ethnic cleansing, the international community has a responsibility to act. R2P represented a significant shift from strict sovereignty norms. In practice it has been applied inconsistently, and its invocation as justification for the 2011 Libya intervention, which led to state collapse, has made subsequent R2P arguments harder.

The right of the five permanent members of the UN Security Council (US, UK, France, Russia, China) to block any resolution regardless of how other members vote. A single veto prevents action. The veto reflects the post-1945 settlement: the major powers would only join the UN if they retained the ability to block decisions against their interests. It means the Security Council cannot act when the major powers disagree, which is frequently.

The body of rules and norms governing relations between states. Treaties, customary international law, rulings of international courts. Unlike domestic law, international law has no reliable enforcement mechanism: compliance depends on states choosing to comply, or on other states imposing costs on those who don't. Critics argue it is therefore not really law. Defenders argue that most states comply with most international law most of the time, which is more than the alternative produces.

The study of how geography shapes politics and power. Mountains, rivers, coastlines, and natural resources determine which states are secure, which are vulnerable, and what they are likely to want. Russia's security anxiety about its flat western border. China's desire for access to warm-water ports. The US's protection by two oceans. Geography does not determine foreign policy, but it constrains and shapes it. Geopolitical analysis is now in wide use in business strategy as well as statecraft.

A state's overarching plan for achieving its long-term national security objectives, coordinating all instruments of power: military, economic, diplomatic, and informational. A grand strategy answers: what are we trying to achieve, and how do we intend to get there? The US strategy of containment during the Cold War was grand strategy. Whether the US has had a coherent grand strategy since is a matter of significant debate.

The thesis advanced by Harvard political scientist Graham Allison: when a rising power threatens to displace a ruling power, war is often the result. Named after the Greek historian's account of the conflict between rising Athens and ruling Sparta that produced the Peloponnesian War. Allison applied the framework to the US-China relationship. Of sixteen historical cases where a rising power challenged a ruling one, twelve resulted in war. The exceptions are what current foreign policy is trying to learn from.

A significant reorientation of foreign policy attention and resources toward a new region or relationship. The Obama administration's "pivot to Asia" in 2011 signalled a strategic shift away from the Middle East and toward the Indo-Pacific, reflecting the assessment that China's rise was the defining challenge of the era. Pivots are as much signals as strategies: they tell allies and adversaries where attention is shifting before the resources do.

The ability to out-escalate an adversary at every rung of the conflict ladder, making further escalation by the opponent irrational. If you can credibly respond to any escalation with a more costly counter-escalation, a rational adversary will not escalate. Escalation dominance requires both capability and credibility. It is one of the key concepts in nuclear strategy but applies to conventional conflict as well. Managing escalation without either backing down or triggering catastrophe is one of the hardest problems in statecraft.