From the Document: "Since May 2019, U.S.-Iran tensions have heightened significantly, and evolved into conflict after U.S. military forces killed Qasem Soleimani, the commander of the Iran's Islamic Revolutionary Guard Corps-Quds Force (IRGC-QF) and one of Iran's most important military commanders, in a U.S. airstrike in Baghdad on January 2, 2020. In 2018, the Trump Administration withdrew from the 2015 multilateral nuclear agreement with Iran (Joint Comprehensive Plan of Action, JCPOA), and since mid-2019 has taken several steps in its campaign of applying 'maximum pressure' on Iran. Apparently in response to the maximum pressure campaign, Iran and Iran-linked forces have attacked and seized commercial ships, caused destruction of some critical infrastructure in the Arab states of the Persian Gulf, attacked facilities used by U.S. military personnel in Iraq, and downed a U.S. unmanned aerial vehicle. As part of an effort its leaders term 'maximum resistance,' Iran has also reduced its compliance with the provisions of the JCPOA. The Administration has been deploying 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/