Iran's national security policy is the product of many, and sometimes competing, factors: the ideology of Iran's Islamic revolution; Iranian leaders' perception of threats to the regime and to the country; long-standing Iranian national interests; and the interaction of the Iranian regime's various factions and constituencies. One aspect of Iran's national security strategy is to take advantage of opportunities of regional conflicts overturn a power structure in the Middle East that Iran asserts favors the United States and its allies Israel, Saudi Arabia, and other Sunni Muslim Arab regimes. Iran characterizes its support for Shiite and other Islamist movements as support for the "oppressed" and asserts that Saudi Arabia, in particular, is instigating sectarian tensions and trying to exclude Iran from regional affairs. Others interpret Iran as primarily to protect itself from U.S. or other efforts to invade or intimidate it or to change its regime. Iran might additionally be seeking to enhance its international prestige or restore a sense of "greatness" reminiscent of ancient Persian empires. During 2010-2016, Iran's foreign policy also sought to blunt the effects of international sanctions. Iran's policy also seems intended to influence the policies and actions of other big powers, such as those in Europe as well as Russia, as partners of the United States or as antagonists of U.S. actions in the region. Iran employs various national security policy tools, including traditional diplomacy and the public promotion of Iran's values and interests. Of greater concern to U.S. officials is that Iran advances its interests by providing material support to armed groups, some of which conduct acts of international terrorism. For several decades the State Department has described Iran as the leading state sponsor of terrorism. Iran's armed support to Shiite-dominated governments, such as those of Syria and Iraq, and factions such as Lebanese Hezbollah, Houthi rebels in Yemen, and Bahrain militant groups, has fueled Sunni popular resentment. The July 2015 multilateral nuclear agreement with Iran (Joint Comprehensive Plan of Action, JCPOA) eased Iran's international diplomatic isolation and provided Iran with opportunities to emerge as a regional energy and trade hub and to negotiate future weapons buys. Supreme Leader Ali Khamene'i and key hardline institutions, such as the Islamic Revolutionary Guard Corps (IRGC), oppose any compromises of Iran's core goals, but support the reintegration into regional and international diplomacy that is advocated by Iran's elected president, Hassan Rouhani. Some experts predicted that the lifting of sanctions in January 2016 in accordance with the JCPOA would enable Iran to expand its regional influence further, whereas the Obama Administration assessed that the JCPOA would cause Iran to moderate its regional behavior in order not to jeopardize the agreement and its benefits. The Trump Administration has cited Iran's regional "malign activities" and repeated ballistic missile tests to assert that "Iran's provocative actions threaten the United States, [and] the [Middle East] region," and that the JCPOA has failed to address Iran's objectionable behavior beyond its nuclear program. The Administration has, to date, sanctioned additional Iran missile entities, sought to forge a regional coalition to counter Iran, and signed into law new legislation sanctioning Iran's regional activities and missile program. In October President Trump asked Congress and U.S. allies to address the JCPOA's weaknesses, including its lack of curbs on Iran's missile program or on Iran's support for regional armed factions-and threatened to end U.S. participation in the JCPOA unless such steps are taken. However, the President did not outline specific new steps to blunt Iran's regional influence beyond modest new sanctions on the IRGC. Sanctions alone have been ineffective, to date, in reducing Iran's reg