Final answer:
A policy of deterrence through military build-up is called militarism, often exemplified by nuclear deterrence strategies such as Mutual Assured Destruction (MAD) during the Cold War.
Step-by-step explanation:
A policy of deterrence through military build-up is known as militarism. This approach involves states escalating their military capabilities, including the development of nuclear arsenals and intercontinental ballistic missiles (ICBMs), to prevent adversaries from considering aggressive military action. This strategy was prominently used during the Cold War, leading to what is referred to as the Mutual Assured Destruction (MAD) doctrine, a form of nuclear deterrence. Nuclear deterrence is based on the idea that the possession of a powerful nuclear capability would deter an adversary from launching an attack due to the mutually guaranteed catastrophic destruction that would ensue.