Relations between Iran and the United States have always been either frigid or antagonistic in nature since the Islamic Revolution. Over the past 43 years, some Iranian reformist officials have sought to de-escalate tensions and reestablish normal relations with the United States. In this study, five milestones in Iran's détente policy are examined. These cases include Iran's mediation in securing the release of American hostages in Lebanon, Iran's lucrative economic offer to the American oil company Conoco, Iran's intelligence assistance to the US in Afghanistan to combat terrorism, the submission of the so-called "Grand Bargain" proposal to negotiate and settle all points of contention with the United States—such as support for Hezbollah and Iran's presence in Iraq—and, finally, the JCPOA. In this study, using the "Process Tracing" method and analyzing primary sources such as US congressional records and IAEA reports, the factors influencing these cases are discussed in detail, and ultimately, the failure or ineffectiveness of each measure is presented through the words of American officials. The analysis of the détente cases supports the theory of "Empire, Client, Enemy States," demonstrating that rapprochement with Iran—which is considered an enemy state by the US—whether strategic, political, or economic, is likely to fail until the internal power structures in Iran and the nature of the Islamic Revolution change, and Iran's role toward the United States shifts from that of an enemy to a client state.