The last time the United States reacted forcefully to the Guards’ aggression was in 1987. When the Guards began mining the Persian Gulf, the United States Navy boarded and sank one of its mining vessels and destroyed several of its speedboats and oil platforms. Our attacks deterred the Revolutionary Guards Corps; it has never again tried to mine the gulf.

More significantly for today, our hard response didn’t diminish Iranian diplomats’ desires to negotiate. At the time, I was the State Department legal adviser, negotiating claims between our two countries that dated to the Iranian revolution, at the United States-Iran arbitration tribunal operating at The Hague. After the Navy acted, I assumed Iran’s diplomats would not want to talk, but I was mistaken. When I canceled the next scheduled meeting, my Iranian counterpart urged me, instead, to keep negotiating. We did, and went on to settle thousands of claims and political questions. Each time the United States has used force in the Middle East — in Kuwait, Afghanistan and Iraq — Iran has sought to be more, not less, engaged diplomatically.

Iran’s 1979 Constitution created the Revolutionary Guards to protect and extend the nation’s Islamic character. The organization has its own army, navy, air force, intelligence operations and police, along with extensive commercial holdings and supervision of Iran’s nuclear and missile programs. Its influence with Iran’s leaders has been enormous, in part because it has played a central role in building an Iranian sphere of influence with Shiite Muslims in Lebanon, Iraq and Syria.

As in Syria today, the Guards’ strategic role has always been marked by force and terror. But (except for 1987) the United States has failed to respond to its violence; we mounted no effective response to the deaths of some 1,000 Americans in attacks traced to the Guards over three decades — on the American Embassy and Marine barracks in Lebanon in 1983, at the Khobar Towers in Saudi Arabia in 1996 and during the wars in Iraq and Afghanistan.

Today, Mr. Rouhani’s team vies with the Guards for the support of Iran’s supreme religious leader, Ayatollah Ali Khamenei. The Guards can argue to him that compromising with America is unnecessary — that history shows Iran can get away with anything. So when American inaction reinforces that impression, it sends exactly the wrong message. Instead, we have to respond to the Guards in such a way that Mr. Rouhani and his team can argue convincingly that the force’s aggression invites only more trouble, while a nuclear deal holds the key to improving Iran’s future.