ELI LAKE: John Bolton Is Exactly What Trump’s Iran Policy Needs.

Iran has historically attacked U.S. targets with its proxies when it assesses it will not face direct military reprisals. Iran used proxy forces to lay roadside bombs during the U.S. war in Iraq, for example, because its judgment at the time was that Bush lacked the support, in Congress or with the public, to respond with a strike inside Iranian territory. (In retrospect, this assessment was correct.) When Iran believes the U.S. will use force, however, it backs off. Iran has not mined the Persian Gulf, despite occasional threats to do so, because the U.S demonstrated three decades ago that it will destroy the Iranian navy if it tries.

This is where Bolton comes in: He’s kind of a one-man psychological warfare operation. If Iran’s leaders believe Trump’s advisers are trying to constrain him, they may assess they can get away with a proxy attack on U.S. positions. If they think Trump is trying to constrain his national security adviser, they may decide not to.

It’s generally beneficial to your diplomatic efforts if you have a pit bull straining at the leash.