President Ronald Reagan warned in 1986 that if Nicaragua’s “Sandinistas” remained in power, “terrorists and subversives” would have sanctuary “just 2 days’ driving time from Harlingen, Texas.” During the 1980s, Reagan gave more speeches on the Central American country than about almost any other foreign policy issue. Congress voted countless times on his policy of undermining Nicaragua’s Cuban- and Soviet-backed government by arming insurgents known as the Contra. White House officials said the stakes were tremendous...