Why is preserve world peace and security important to the mission of the UN.

The UN accomplishes this by working to prevent conflict, helping parties in conflict make peace, deploying peacekeepers, and creating the conditions to allow peace to hold and flourish. ... The UN Security Council has the primary responsibility for international peace and security.

ok

explanation:

roosevelt believed that in light of the country's recent military successes, it was unnecessary to use force to achieve foreign policy goals, so long as the military could threaten force. this belief, and his strategy of “speaking softly and carrying a big stick,” shaped much of roosevelt's foreign policy.