From the Introduction: "Since 2017, the United States and some of its major trading partners have engaged in a contentious 'war' of words over trade--one that tipped over into action in February 2018, mostly in the form of increased tariffs. The tariffs imposed by the Trump Administration, combined with retaliatory measures adopted by other countries, are reportedly having noticeable effects on trade flows and U.S. firms. Although the scale and scope of these recent unilateral U.S. tariff increases are unprecedented in modern times, tensions and irritants in international trade relations are not uncommon. Over the last 100 years, the United States has been involved in a number of trade disputes. According to the World Trade Organization (WTO), as of July 2019, the United States is currently involved in 278 active trade disputes being addressed in the WTO dispute settlement system-- either as complainant or as a respondent. Most disputes are settled, or when unresolved, are contained or defused through bilateral and multilateral negotiations. From the early 20th century until this year, only one resulted in a worldwide tit-for-tat escalation of tariffs: the trade dispute ignited by the U.S. 'Smoot-Hawley' Tariff Act of 1930."
CRS In Focus, IF10958
Congressional Research Service: https://crsreports.congress.gov/