Arms racing is the suboptimal outcome of a prisoner’s dilemma (all competitors feel compelled to over purchase security).

The prisoner’s dilemma is created by absence of coordination among competitors with a shared interest (states are better off planning for national security according to real rather than systemic considerations [though I’m not sure that the real/systemic distinction is tenable — at some point the system is the real]).

Arms control is the coordination among strategic competitors that allows an escape from the best-bad outcome reasoning of a prisoner’s dilemma.