Security dilemma
Etymology
Coined by the political scientist John H. Herz in 1950, with parallel ideas from the historian Herbert Butterfield. The phrase captures the dilemma in international anarchy where, absent any way to prove peaceful intent, defensive measures are read as offensive ones.
noun phrase · /sih-KYOOR-ih-tee dih-LEM-uh/
The trap in which one state’s efforts to make itself safer appear threatening to others, provoking the very hostility it feared.
What it names
A powerful lens on how arms races and spirals of distrust arise between actors who may each only want defense — a tragedy driven by uncertainty, not malice.
Example
Each new missile battery was purely defensive in its planners’ minds, but the security dilemma ensured the neighbor answered with weapons of its own.
Related idea
A specific geopolitical instance of the collective action problem, where rational individual choices yield a worse outcome for all; here mutual defense-seeking produces mutual insecurity because no one can credibly signal restraint.