(A) all countries agree to attack one country.
(B) ** all countries agree not to attack each other.
(C) all countries do not bother about other countries’ security.
EXPLANATIONS BELOW
Concept note-1: -collective security, system by which states have attempted to prevent or stop wars. Under a collective security arrangement, an aggressor against any one state is considered an aggressor against all other states, which act together to repel the aggressor.
Concept note-2: -Collective defence means that an attack against one Ally is considered as an attack against all Allies. The principle of collective defence is enshrined in Article 5 of the Washington Treaty. NATO invoked Article 5 for the first time in its history after the 9/11 terrorist attacks against the United States.
Concept note-3: -Collective Security: Meaning The basic principle of “one for all and all for one” is the principle underneath it. Andrew Heywood defines it as “the theory or practice of states pledging to defend one another in order to deter aggression or to punish a transgressor if international order has been breached…”1 .
Concept note-4: -The idea behind the collective security system is that members of the organization advancing the collective security system (this time, the United Nations) are bound to spring to each other’s defense in case of attack. The basic principle is that an attack on one is an attack on all.