From the Document: "Since May 2019, U.S.-Iran tensions have escalated, but not erupted into armed conflict. The Trump Administration, following its 2018 withdrawal from the 2015 multilateral nuclear agreement with Iran (Joint Comprehensive Plan of Action, JCPOA), has taken several steps in its campaign of applying 'maximum pressure' on Iran. Iran and Iran-linked forces have targeted and sometimes seized commercial ships, attacked infrastructure in U.S. partner countries, and posed threats to U.S. forces and interests, including downing a U.S. unmanned aerial vehicle. The Administration has sent additional military assets to the region to try to deter future Iranian actions."
CRS Report for Congress, R45795
Congressional Research Service: https://crsreports.congress.gov/