In a policy address at the Council on Foreign Relations last month, Secretary of State Hillary Clinton said of Iran, “We cannot be afraid or unwilling to engage.” But the Iranian government has yet to accept President Obama’s outstretched hand. Even if Tehran suddenly acceded to talks, U.S. policy makers must prepare for the eventuality that diplomacy fails. While there has been much discussion of economic sanctions, we cannot neglect the military’s role in a Plan B.

There has been a lack of serious...