Messrs. Frank and Paul and their supporters have taken it into their minds that a reduced American presence in world affairs, particularly where the military is involved, would be a good thing. They had better think again: World politics, like nature, is hardly prone to respect vacuums. Iran and Venezuela remain as bellicose and destabilizing as ever, in spite of two years of Obama “engagement.” Iran squats beside the Strait of Hormuz, through which much of the world’s energy supply travels. Iran has also, the original Monroe Doctrine be damned, extended its military cooperation with Hugo Chávez’s authoritarian regime. Evidence is strong that Venezuela is providing sanctuary for Hezbollah terrorists in South America. The alliance of these two anti-American and increasingly menacing states could pose a threat to the United States of a kind that would make us nostalgic for the Cuban Missile Crisis.

Faced with such challenges, the United States can ill afford military retrenchment as advocated by the new isolationists. While waste in the Pentagon’s budget can and should be cut, the new isolationists want to do it with a chainsaw when a scalpel is needed. In the last decade, the U.S. Navy’s fleet has shrunk to its smallest size since the 19th century, just as potential rivals such as China have not only expanded theirs but have begun to target perceived American maritime vulnerabilities. The U.S. Air Force is fielding an aging and shrinking force, while China is developing an advanced fighter for sale to adversaries of America, including Iran.