Question

Stay in pact to entail regret or quit to ensure the nation's disarmament?

Answer 1

Fundamentally, Pact is considered as means of an agreement between two parties. Regret means feel sad. entail means involving something. disarmament means basically a part of the peace process.

So here the statement means that you need to maintain fewer wars to ensure peace.

For example, the Paris Peace Conference or pact was formed with the objective of creating a treaty for which  Germany would be punished and meet the objectives of the various Allied Powers. Negotiating the treaty, was a long and complex procedure.