Why alliances deter war?

Alliances deter war by creating a collective security arrangement, where potential aggressors face a unified front of multiple nations, raising the costs and risks of military conflict. This collective defense can discourage hostile actions, as the likelihood of facing a coordinated response makes aggression less appealing. Additionally, alliances often enhance communication and trust among member states, fostering diplomatic solutions to conflicts before they escalate into war. Overall, the presence of alliances increases the strategic calculations against initiating hostilities.