What would the other states do in even one state was attacked?

The response of other states to an attack on one state would depend on various factors, including political alliances, geographic proximity, and the severity of the attack. Here are a few possible scenarios:

1. Mutual Defense Pacts: If the attacked state is part of a mutual defense pact, such as NATO, the other member states would be obligated to come to its defense. This could involve providing military assistance, logistical support, or economic sanctions against the aggressor.

2. Regional Alliances: States that share geographic proximity and common interests may form regional alliances for mutual security. If one member state is attacked, other members may provide assistance based on the terms of their alliance agreements. For instance, within the European Union, the principle of solidarity and the mutual defense clause (Article 42.7 of the Treaty on European Union) could trigger collective action.

3. Coordinated Diplomatic Response: States may collectively condemn the attack through diplomatic channels, such as the United Nations Security Council. They may impose economic sanctions, travel restrictions, or diplomatic isolation on the aggressor state to pressure it to cease hostilities and comply with international law.

4. Limited Involvement: Some states may choose to provide limited assistance, such as humanitarian aid or intelligence sharing, without directly engaging in military conflict. This approach may aim to avoid escalating the situation or becoming embroiled in a wider conflict.

5. Neutrality: Other states may choose to remain neutral, avoiding taking sides in the conflict and attempting to maintain good relations with both the attacked state and the aggressor.

6. Unilateral Action: In certain cases, a powerful state may take unilateral action to defend its interests or maintain regional stability. This could involve deploying military forces, conducting air strikes, or providing covert support to the attacked state.

7. Escalation: In the worst-case scenario, an attack on one state could lead to a wider regional or even global conflict. This could happen if the aggressor retaliates against the defending states, or if other states become involved due to their alliances or interests.

Ultimately, the response of other states would be shaped by a combination of legal obligations, political calculations, and the particular circumstances of the attack.