One of the main challenges of maintaining peaceful international relations is the escalation of distrust and the ensuing arms race.

The possibility that others might attack you is a reason to arm yourself. But this step will in turn be interpreted as a threat by the other, who will in turn arm itself (even more). Etc.

Aren’t there ways to simply invest in purely defensive weapons? So that your efforts to remain safe do not in turn threaten others? Which in turn allows others to also de-escalate?

In other words, are there military set-ups that are useless for offensive actions but good enough for defending a country?