NATO members should defend attacked allies even at risk of war with a nuclear power

Study and practice of how sovereign states, international institutions, and non-state actors interact across borders. Encompasses diplomacy, negotiation, alliances, and conflict — the foundational domain through which global order is constructed, contested, and maintained.

The alliance's cooperation with Western partners: collective defence and deterrence, defence-industrial and technology investment, burden-sharing and the coordination of military support among member states and allied governments.

Security arrangement under which states commit to treat an attack on one as an attack on all, obliging joint response. Underpins alliances such as NATO and provisions of the UN Charter, making shared deterrence and coordinated military planning central instruments of international stability.